What Is GNSS? Global Navigation Satellite System

Every time a phone provides driving directions, a surveyor measures a property boundary, or a scientist tracks the movement of a tectonic plate, satellites thousands of kilometers above Earth may be involved. The technology behind these measurements is called GNSS, or Global Navigation Satellite System.

GNSS is actually a broader term than GPS. GPS, operated by the United States, is one GNSS constellation. Other systems include Europe's Galileo, China's BeiDou, and Russia's GLONASS. Modern receivers can often communicate with several constellations, providing more satellites and improving positioning reliability.

How Does GNSS Find Your Location?

GNSS satellites continuously transmit radio signals containing extremely precise timing and orbital information.

A receiver—such as your phone—records when a signal arrives. Because radio waves travel at approximately the speed of light, the receiver can estimate its distance from a satellite using:

Distance ≈ speed of light × signal travel time

Knowing your distance from one satellite is not enough to determine your location. Instead, a GNSS receiver simultaneously measures signals from multiple satellites.

At least four satellites are normally needed to solve for four unknowns: your three-dimensional position—latitude, longitude, and altitude—and the timing error in the receiver's clock.

This process is commonly called trilateration.

Why Isn't Your Phone Perfectly Accurate?

GNSS positioning sounds straightforward, but the signals encounter several problems while traveling to Earth's surface.

The ionosphere and troposphere can delay radio signals. Satellite orbit and clock uncertainties introduce additional errors. Buildings, mountains, and other objects can reflect signals before they reach a receiver, producing an effect called multipath.

This is why a smartphone might place you on the wrong side of a street even though GNSS itself can achieve much greater precision.

Professional geodetic receivers use sophisticated techniques to correct these errors. Differential GNSS compares observations from receivers at known locations, while Real-Time Kinematic (RTK) positioning uses measurements of the signal's carrier wave to achieve centimeter-level positioning under favorable conditions.

GNSS Can Measure a Moving Earth

GNSS becomes particularly interesting when it is used for geodesy.

Permanent GNSS stations installed on stable ground continuously record their positions. By comparing measurements across months or years, scientists can detect extremely small movements of Earth's crust.

For example, tectonic plates may move only a few centimeters each year. That movement sounds insignificant, but GNSS stations can measure it. Networks of receivers therefore allow geodesists to map plate motion and study how strain accumulates around faults.

After major earthquakes, GNSS can also reveal how far the surface moved.

Measuring Glaciers, Volcanoes, and Sea Level

GNSS has applications far beyond navigation.

Researchers can install receivers on glaciers to measure how quickly the ice flows. Stations around volcanoes can detect ground inflation or deflation caused by magma moving underground. GNSS measurements are also combined with tide gauges to separate changes in ocean height from movement of the land itself.

Even Earth's atmosphere can be studied using GNSS. Scientists analyze how satellite signals are delayed as they travel through atmospheric water vapor, providing information useful for meteorology.

More Than a Navigation System

GNSS has effectively created a continuously available global measurement framework.

A technology most people encounter as the blue location dot on their phones can measure processes occurring across an extraordinary range of scales—from tracking a moving vehicle to detecting the slow deformation of an entire continent.

For geodesy, that is what makes GNSS so powerful. It doesn't simply tell us where something is. By repeatedly measuring position with extreme precision, it tells us how Earth itself is moving and changing over time.

Earth System Evolution Dynamics

Earth today—with blue oceans, oxygen-rich air, continents, glaciers, and abundant life—is only one version of our planet. Over its roughly 4.5-billion-year history, Earth has continuously evolved as its atmosphere, oceans, rocks, ice, and living organisms interacted. Understanding these connections is the focus of Earth system science, which treats the planet not as separate environments but as one enormous dynamic system.

Earth can be divided into several interconnected components: the geosphere (rocks and Earth's interior), hydrosphere (water), atmosphere (air), cryosphere (ice), and biosphere (life). A change in one can trigger changes throughout the others.

A Planet Built by Feedback Loops

One of the most important concepts in Earth system dynamics is the feedback loop.

Consider ice. Snow and glaciers have high albedo, meaning they reflect large amounts of incoming sunlight. If global temperatures decrease, ice can expand. More ice increases Earth's reflectivity, causing less solar energy to be absorbed and encouraging additional cooling.

The same process can operate in reverse. Warming melts ice, exposing darker ocean or land underneath. Those surfaces absorb more solar energy, potentially causing additional warming. This is known as ice-albedo feedback.

Other feedbacks involve vegetation, clouds, atmospheric water vapor, oceans, and the carbon cycle. Some amplify an initial change, while others counteract it.

The Continents Are Constantly Moving

Earth's solid surface is also dynamic.

Plate tectonics continuously moves continents, creates mountains, opens and closes oceans, produces volcanoes, and recycles crust into Earth's mantle. Over hundreds of millions of years, these processes can completely reorganize the planet.

Continental position can even influence climate. Moving land toward the poles can create environments where large ice sheets develop. Mountain building alters atmospheric circulation and rainfall. Meanwhile, volcanic eruptions transfer carbon dioxide from Earth's interior into the atmosphere.

Plate tectonics also interacts with the long-term carbon cycle. Carbon dioxide dissolves in rainwater and participates in chemical weathering of rocks. Some of that carbon eventually reaches the oceans, where it can become incorporated into carbonate minerals and sediments. Tectonic processes eventually recycle some of this material into Earth's interior.

This creates a carbon cycle operating over millions of years.

Life Changed the Planet

Perhaps the most extraordinary example of Earth system evolution is that life itself transformed Earth.

Early Earth's atmosphere contained extremely little free oxygen. Beginning billions of years ago, photosynthetic microorganisms released oxygen as a byproduct. Eventually, oxygen began accumulating in the atmosphere during what scientists call the Great Oxidation Event.

This atmospheric transformation changed ocean chemistry, mineral formation, and biological evolution.

Life has continued modifying the planet ever since. Plants influence atmospheric carbon dioxide, forests affect rainfall and evaporation, marine organisms contribute to carbon storage, and microorganisms drive chemical cycles involving carbon, nitrogen, and sulfur.

From Greenhouse Worlds to Snowball Earth

Earth's climate has never been constant.

At different points in geological history, the planet experienced extremely warm greenhouse climates with little permanent polar ice. At other times, glaciers expanded dramatically. During several episodes hundreds of millions of years ago, ice may have reached tropical latitudes, producing conditions commonly associated with Snowball Earth.

These transitions demonstrate that Earth's systems can cross important thresholds. A relatively small initial forcing can sometimes trigger much larger changes through feedback mechanisms.

A Planet That Never Reaches a Final State

Modern satellites, ocean sensors, GNSS stations, ice cores, sediment cores, fossils, and computer models allow scientists to investigate these interactions across timescales ranging from seconds to billions of years.

The central lesson of Earth system evolution is that nothing operates completely independently. Tectonics affects climate. Climate influences glaciers. Glaciers reshape landscapes. Oceans redistribute heat. Life alters the atmosphere, and the atmosphere influences life.

Earth is therefore less like a static collection of environments and more like a continuously evolving network. Understanding those connections helps explain not only how the planet reached its present state, but also how today's changes could shape the Earth of the future.

Tidally Locked Moon

No matter when you look at the Moon from Earth, you see essentially the same collection of craters, mountains, and dark volcanic plains. We never naturally get a direct view of the opposite hemisphere from Earth's surface. This happens because the Moon is tidally locked to Earth, one of the most interesting consequences of gravity in our solar system.

Tidal locking does not mean the Moon has stopped rotating. In fact, the opposite is true: the Moon rotates once on its axis in approximately 27.3 days, almost exactly the same amount of time it takes to complete one orbit around Earth. Because these two periods match, the same hemisphere continually faces us.

How Did the Moon Become Tidally Locked?

The Moon probably did not begin this way.

Early in its history, the Moon likely rotated much faster. Earth's gravity, however, does not pull equally strongly on every part of the Moon. The side facing Earth experiences a slightly stronger gravitational attraction than the opposite side.

This difference produces a tidal force.

When the young Moon rotated more rapidly, Earth's tidal forces slightly distorted its shape. Because the Moon was rotating, this tidal bulge was not always perfectly aligned with Earth. Earth's gravity pulled on the misaligned bulge, creating a torque that gradually slowed the Moon's rotation.

Eventually, the rotation period matched its orbital period. At that point, the tidal bulge remained approximately aligned with Earth, producing the stable configuration we observe today.

This state is called synchronous rotation.

The “Dark Side” Isn't Actually Dark

The hemisphere facing Earth is called the near side, while the opposite hemisphere is the far side.

Calling the far side the "dark side of the Moon" is misleading. It receives approximately the same amount of sunlight as the near side. During a new moon, for example, the far side is largely illuminated while the near side faces away from the Sun.

Humanity did not see the far side until the Soviet Luna 3 spacecraft photographed it in 1959.

Those images revealed something surprising: the two sides look dramatically different. The near side contains large dark regions called maria, created by ancient lava flows. The far side contains far fewer maria and is dominated by heavily cratered highlands.

Scientists continue investigating why the Moon developed this geological asymmetry.

Is Exactly 50% of the Moon Visible?

Interestingly, tidal locking doesn't restrict us to exactly half of the lunar surface.

The Moon's orbit is slightly elliptical, and its orbital speed changes as it travels around Earth. Meanwhile, its rotation remains relatively steady. Combined with the Moon's tilted orbit and our changing viewing position, this produces an apparent rocking motion called libration.

Over time, libration allows observers on Earth to see about 59% of the Moon's surface, although only roughly half is visible at any single moment.

Tidal Locking Happens Across the Solar System

Our Moon is far from unique. Many large moons in the solar system are tidally locked to their planets, including Europa around Jupiter, Titan around Saturn, and Triton around Neptune.

The same physics may even affect exoplanets. Planets orbiting close to small red-dwarf stars can experience strong tidal forces and may eventually become tidally locked, potentially producing permanent daysides and nightsides.

Earth and the Moon are still exchanging angular momentum today. Tidal interactions cause the Moon to move away from Earth by about 3.8 centimeters per year, a rate measured using lasers reflected from mirrors left on the lunar surface.

The familiar face we see in the night sky is therefore not a coincidence. It is the result of billions of years of gravitational interaction, slowly synchronizing the Moon's rotation with its journey around our planet.

Analyzing Exoplanet Cryospheres

When scientists discuss the cryosphere, they usually mean Earth's glaciers, ice sheets, sea ice, permafrost, and seasonal snow. But the same idea can be extended far beyond our solar system. Thousands of confirmed exoplanets orbit other stars, and some may contain enormous quantities of frozen water or other ices. Studying these hypothetical exoplanet cryospheres could help scientists understand planetary climates—and determine which distant worlds might be capable of supporting liquid water.

The challenge is obvious: we cannot currently photograph glaciers on an Earth-sized planet dozens of light-years away. Instead, scientists have to combine astronomical observations with climate models, spectroscopy, and planetary physics.

Where Would Ice Form?

The first clue comes from a planet's orbit and its star.

A planet receiving little stellar radiation could maintain extensive surface ice. But distance alone does not determine whether a planet freezes. Atmospheric composition, pressure, rotation, ocean circulation, cloud cover, and surface reflectivity can dramatically change temperature.

Researchers can feed these variables into general circulation models (GCMs)—similar to models used to simulate Earth's climate. These simulations divide a planet's atmosphere and surface into a three-dimensional grid and calculate how energy, air, and sometimes oceans move between regions.

Scientists can then ask fascinating questions: Would glaciers develop near the poles? Could an entire ocean freeze? Would an equatorial region remain ice-free?

The Snowball Planet Problem

One important process is ice-albedo feedback.

Ice and snow reflect a large percentage of incoming radiation. If a planet begins cooling and its ice expands, the brighter surface reflects more energy back into space. That causes additional cooling, potentially producing even more ice.

Under certain conditions, models suggest an Earth-like exoplanet could enter a "snowball" state, with ice covering most or all of its oceans. Earth itself appears to have experienced extreme global glaciations hundreds of millions of years ago, making our planet an important comparison for these simulations.

But a frozen surface does not necessarily mean a completely frozen planet.

A thick ice layer could insulate liquid water underneath, especially if heat continues escaping from the planet's interior. Similar environments already exist within our own solar system on icy moons such as Europa and Enceladus.

Can We Actually Detect Exoplanet Ice?

Direct detection remains extremely difficult, but future observations may provide clues.

When an exoplanet passes in front of its star, telescopes can analyze how different wavelengths of light interact with its atmosphere. Spectroscopy can reveal molecules such as water vapor, carbon dioxide, and methane, helping researchers constrain possible surface conditions.

Reflected light could eventually provide another clue. Snow, ocean water, rock, and vegetation reflect different wavelengths differently. A sufficiently powerful future telescope might detect spectral patterns consistent with extensive surface ice.

Astronomers must be careful, however. Clouds can also make planets highly reflective, creating a major challenge when trying to distinguish an icy surface from a cloudy atmosphere.

Glaciers on Tidally Locked Worlds

Some especially interesting possibilities involve planets orbiting red dwarf stars.

Planets close to these relatively cool stars may become tidally locked, meaning one hemisphere permanently faces the star while the other remains in darkness. Climate simulations suggest this could produce unusual cryospheres. Water might freeze on the permanent nightside while remaining liquid near the warmer region facing the star.

Ice could therefore physically redistribute a planet's water over geological time, potentially creating enormous glaciers unlike anything found on modern Earth.

Using Earth's Ice to Understand Alien Worlds

This is where glaciology, astronomy, geophysics, and computer science increasingly overlap. Researchers can use what we know about ice flow, albedo, atmospheric circulation, geothermal heating, and glacier mass balance to simulate environments we cannot directly visit.

Exoplanet cryosphere research ultimately reverses the usual way we think about glaciers. Instead of only asking what ice tells us about Earth's climate, scientists can ask a much bigger question:

What can ice tell us about whether an entirely different planet could be habitable?

Modeling the Carbon Cycle

Carbon is constantly moving around our planet. A carbon atom released from a forest fire might enter the atmosphere as carbon dioxide, dissolve into the ocean years later, become incorporated into marine life, and eventually settle into sediments on the seafloor. This enormous network of exchanges is known as the carbon cycle, and computer science is becoming increasingly important for understanding how it is changing.

The carbon cycle can be thought of as a giant computational system. Scientists divide Earth into major carbon reservoirs, including the atmosphere, oceans, vegetation, soils, sediments, and rocks. Carbon then moves between these reservoirs through processes such as photosynthesis, respiration, decomposition, ocean-atmosphere exchange, weathering, and volcanic activity.

The challenge is that these processes operate on dramatically different spatial and temporal scales. Photosynthesis can change atmospheric carbon concentrations seasonally, while geological carbon storage can operate over millions of years. This is where computational modeling becomes essential.

Turning Earth Into a Mathematical Model

At its simplest, a carbon-cycle model can represent each reservoir as a variable.

Imagine a basic model containing only the atmosphere, land, and ocean. Every simulated year, the computer calculates how much carbon moves between them. Plants remove CO₂ through photosynthesis, respiration returns some carbon to the atmosphere, and the ocean simultaneously absorbs and releases CO₂.

The model updates each reservoir repeatedly:

New carbon = existing carbon + carbon entering − carbon leaving

Real Earth-system models perform versions of this calculation across millions of grid cells while also considering temperature, rainfall, ocean circulation, vegetation, soil chemistry, and human emissions.

That requires enormous computing power.

Satellites Create a Data Problem

Computer science is also transforming where carbon-cycle models get their information.

NASA's Orbiting Carbon Observatory-2 (OCO-2) measures atmospheric carbon dioxide from space, while other Earth-observing missions provide information about vegetation, fires, ocean conditions, temperature, and land cover. Together, these instruments generate enormous datasets that would be difficult to analyze manually.

Algorithms can combine these observations with ground measurements and models to estimate where carbon is being emitted and absorbed.

This produces what scientists sometimes describe as carbon "sources" and "sinks." A forest that absorbs more carbon than it releases acts as a sink, while fossil-fuel combustion is a major source.

Machine Learning Enters the Carbon Cycle

One emerging area involves machine learning.

Instead of explicitly programming every environmental relationship, researchers can train algorithms on observations and simulations to recognize patterns. Machine-learning models can help estimate forest carbon storage, predict ecosystem productivity, detect land-use changes, and approximate computationally expensive components of climate models.

However, AI does not eliminate the need for physical science. A model might find a statistical relationship that works under present conditions but fails as Earth's climate moves into conditions absent from its training data. Combining physics-based models with machine learning is therefore an important research direction.

Debugging a Planet

Perhaps the most interesting connection between computer science and carbon-cycle science is uncertainty.

Scientists cannot simply run one simulation and assume it represents Earth's future. They may run models thousands of times while changing emissions, climate sensitivity, ecosystem responses, or ocean behavior.

In a sense, researchers are continuously debugging a digital version of Earth—comparing its output against satellites, atmospheric stations, ocean measurements, and historical records.

The better these computational models become, the better we can understand where human-produced carbon goes, how long it remains there, and how Earth's oceans and ecosystems may respond in the future.

SpaceX Reusable Rockets

For most of spaceflight history, launching a rocket has meant throwing away a remarkably expensive machine after only a few minutes of use. SpaceX is attempting to change that model with Starship, an enormous launch system designed around one central idea: make essentially the entire rocket reusable.

Starship consists of two stages. The lower Super Heavy booster provides the enormous thrust required to escape the lower atmosphere, while the upper-stage spacecraft—also called Starship—continues toward orbit. SpaceX's newer Version 3 system uses Raptor 3 engines, which burn liquid methane and liquid oxygen. On Starship's 13th flight test in July 2026, Super Heavy ignited all 33 of its engines for liftoff. 

Why Methane?

Starship's choice of methane (CH₄) is particularly interesting for long-duration space exploration.

Methane engines can be designed for reuse while producing less soot than kerosene-burning engines. Even more importantly, methane could potentially be manufactured away from Earth. Mars has an atmosphere dominated by carbon dioxide, while water ice exists beneath and around its surface. Through chemical processes such as the Sabatier reaction, hydrogen derived from water can react with carbon dioxide to produce methane.

A future Mars mission could therefore theoretically manufacture part of its return propellant on Mars rather than carrying all of it from Earth.

Catching a Rocket Instead of Landing It

One of Starship's strangest engineering features is its recovery system. Rather than always landing Super Heavy on conventional landing legs, SpaceX has demonstrated catching boosters with enormous mechanical arms attached to its launch tower.

The concept removes the mass of traditional landing legs and could eventually allow a recovered booster to be rapidly inspected, refueled and flown again. SpaceX sees rapid reuse as essential to making very high launch rates practical.

This is where Starship differs fundamentally from most previous rockets. A reusable rocket isn't truly revolutionary if rebuilding and inspecting it takes months. SpaceX is ultimately trying to make rocket operations behave more like aircraft operations, where the vehicle lands, is serviced and flies again.

Refueling a Spacecraft in Space

Reusability alone isn't enough for Starship's most ambitious missions. Traveling to the Moon or Mars requires enormous amounts of energy, so SpaceX plans to refuel Starship in Earth orbit.

A tanker Starship would launch propellant into orbit and transfer extremely cold liquid methane and oxygen to another spacecraft. This presents major engineering challenges because cryogenic liquids behave differently in microgravity and continuously absorb heat from their surroundings.

NASA's inspector general has identified large-scale vehicle-to-vehicle cryogenic propellant transfer as one of the most significant technical challenges facing the Starship lunar program.

From Earth Orbit to the Moon

Starship is also connected directly to NASA's future lunar exploration.

NASA is developing a specialized Starship Human Landing System (HLS) with SpaceX. The lunar version is roughly 50 meters tall and is intended to transport astronauts between lunar orbit and the Moon's surface during future Artemis missions. NASA is currently conducting additional testing, including wind-tunnel studies of the Version 3 Super Heavy configuration.

Starship remains an experimental system, and important capabilities—including routine rapid reuse and the full orbital-refueling architecture—still have to be demonstrated. But that experimentation is also what makes the project scientifically and technologically interesting.

If its major engineering goals can be achieved, Starship could change more than how rockets look. Large payload capacity, orbital refueling and rapid reusability could change what kinds of missions are physically and economically possible, from giant space telescopes and lunar laboratories to much more ambitious exploration of Mars.

What Can We Learn From Ice Cores?

Thousands of meters beneath the surfaces of Antarctica and Greenland lies one of Earth's most detailed environmental archives. Ice cores are long cylinders of ice drilled from glaciers and ice sheets, with the deepest cores containing snow that fell hundreds of thousands—or even more than a million—years ago.

Unlike many geological records, ice preserves more than evidence of past temperatures. It can trap ancient air, volcanic ash, dust, sea salt, pollutants, and chemical compounds, allowing scientists to reconstruct entire environments that disappeared long before humans began recording weather.

Ancient Air Trapped Inside Ice

Perhaps the most remarkable feature of an ice core is its tiny air bubbles.

When snow falls, air initially circulates through spaces between snowflakes. As additional snow accumulates, the deeper layers become compressed into dense glacial ice. Eventually, the pathways between the grains close, trapping small samples of the atmosphere.

Scientists can extract these gases and directly measure past concentrations of carbon dioxide, methane, and nitrous oxide.

Antarctic ice cores have provided continuous atmospheric greenhouse-gas records extending back around 800,000 years, while newer projects are recovering ice extending beyond one million years. These measurements reveal repeated relationships between greenhouse gases and Earth's glacial-interglacial climate cycles.

Reconstructing Ancient Temperatures

The ice itself provides another climate signal.

Water contains different isotopes of oxygen and hydrogen. During evaporation, condensation, and snowfall, heavier and lighter isotopes behave slightly differently depending partly on temperature.

Scientists therefore measure ratios such as oxygen-18 to oxygen-16 or deuterium to hydrogen within individual ice layers. After careful calibration, these ratios provide information about past temperature and atmospheric circulation.

By measuring thousands of sections down a core, researchers can reconstruct temperature changes across enormous periods.

Finding Ancient Volcanic Eruptions

Volcanoes can leave surprisingly clear signatures in ice.

Major eruptions inject sulfur dioxide and ash into the atmosphere. Sulfur dioxide can form sulfate aerosols, which eventually fall onto polar ice sheets and become buried by later snowfall.

Sharp increases in sulfate concentrations can therefore reveal previously known—and sometimes previously unidentified—eruptions.

Researchers can compare volcanic layers between Greenland and Antarctica to determine whether an eruption's atmospheric effects were regional or widespread. These records also help scientists investigate whether major eruptions corresponded with periods of temporary global cooling.

Dust Reveals Lost Landscapes

Even microscopic pieces of dust contain information.

During cold glacial periods, stronger winds and drier landscapes often transported substantially more mineral dust toward the polar regions. Scientists can analyze the chemistry and mineral composition of particles trapped within ice to determine where they originated.

Ice cores can consequently reveal changes occurring thousands of kilometers away, including shifts in deserts, winds, atmospheric circulation, and vegetation.

Human Activity Is Preserved Too

The newest layers tell a different story.

Ice cores preserve evidence of lead pollution, industrial chemicals, radioactive material from nuclear testing, and fossil-fuel emissions. In some locations, scientists can even detect changes associated with historical mining and metal production.

An ice sheet therefore acts almost like a natural environmental hard drive.

Each layer adds information to the previous one: temperature, snowfall, atmospheric composition, volcanic eruptions, wind patterns, pollution, and more.

By drilling downward, scientists are effectively traveling backward through Earth's climate system. And because understanding future climate change requires knowing how the planet behaved in the past, some of our best clues about Earth's future are being discovered inside ice that has remained frozen for hundreds of thousands of years.

Computer Vision Applications in Geodesy Today

Geodesy has traditionally relied on instruments such as GNSS receivers, total stations, radar satellites, and laser scanners to measure Earth's shape and how its surface changes. But another technology is rapidly becoming part of the geodetic toolbox: computer vision.

Computer vision allows computers to extract measurements and patterns from photographs, satellite imagery, and video. Combined with artificial intelligence, it can transform huge collections of images into information about surface movement, elevation, glaciers, earthquakes, and infrastructure deformation.

Turning Photographs Into 3D Terrain

One of the most useful applications is Structure from Motion (SfM) photogrammetry. Instead of directly measuring millions of points, researchers take overlapping photographs of an area from different positions.

Computer-vision algorithms identify matching features between photographs and use their changing positions to calculate depth. Thousands of images can therefore be converted into dense 3D point clouds, digital elevation models (DEMs), and orthomosaics.

Drones make this especially powerful. Researchers can repeatedly fly the same route over a landslide, glacier, coastline, or fault and construct a new 3D model during every survey.

Comparing those models reveals changes that would be difficult to recognize from photographs alone.

Watching Glaciers Move

Glaciology is particularly well suited to computer vision because glacier surfaces contain recognizable features such as crevasses, debris, and cracks.

Feature-tracking algorithms can identify the same surface patterns in satellite images taken days or weeks apart. Their displacement between images reveals how far the ice moved.

This creates glacier velocity maps covering enormous regions without requiring instruments directly on the ice. Similar techniques can track changes in glacier termini and automatically identify expanding or shrinking glacial lakes.

Machine-learning systems are also becoming increasingly capable of separating snow, ice, rock, water, and shadows in satellite imagery. This could make monitoring thousands of glaciers considerably faster.

Measuring Earthquakes from Images

Computer vision can also help geodesists study earthquakes.

When an earthquake shifts the ground horizontally, features such as roads, river channels, fields, and ridges can move between pre- and post-earthquake satellite images. Image correlation measures these offsets across thousands of locations.

The result is essentially a displacement map created from photographs.

These measurements complement GNSS and InSAR. GNSS provides extremely precise movement at individual stations, while InSAR measures deformation using radar phase differences. Optical computer vision can provide another perspective, particularly where very large ground movements make radar measurements difficult.

AI Could Make Geodetic Monitoring Continuous

Perhaps the most interesting emerging application is combining computer vision with the enormous volume of imagery now produced by Earth-observing satellites.

Traditionally, researchers might manually select images and analyze a specific glacier or landslide. An AI-based system could instead continuously examine new imagery and automatically flag unusual changes.

A model might detect a rapidly accelerating glacier, newly forming glacial lake, expanding landslide, coastal erosion, or surface rupture and direct researchers toward the event.

This creates the possibility of moving from periodic surveying toward near-continuous geodetic monitoring.

Smartphones May Become Geodetic Instruments

Computer vision could even expand geodesy beyond specialized scientific equipment. Modern smartphones contain high-resolution cameras, GNSS receivers, accelerometers, gyroscopes, and, in some models, LiDAR sensors.

Researchers are experimenting with using these sensors to construct local 3D models and measure structures. Although smartphones cannot replace survey-grade GNSS or terrestrial laser scanners for the highest-precision measurements, they could make rapid mapping dramatically more accessible.

The future of geodesy may therefore involve an increasingly powerful combination:

GNSS provides position. Radar measures deformation. LiDAR measures geometry. Computer vision interprets what is changing.

Together, these technologies could allow scientists to observe Earth's surface at a scale and frequency that traditional surveying alone could never achieve.

What are the Aleutian Islands?

Stretching in a dramatic arc from the Alaska Peninsula toward Russia, the Aleutian Islands are one of the clearest places on Earth to see the connection between deep-Earth geology and the frozen surface. The roughly 3,000-kilometer Aleutian arc exists because two enormous tectonic plates are colliding beneath the North Pacific. But after volcanoes built these islands, cold temperatures and heavy snowfall allowed glaciers to become another major force shaping their landscapes.

Building an Island Chain from Below

The Aleutians sit along a subduction zone, where the dense oceanic Pacific Plate moves beneath the North American Plate. Today, the Pacific Plate moves northwest relative to North America at roughly 55–75 millimeters per year, depending on location along the arc.

As the descending plate travels deeper into Earth, it releases water into the hot mantle above it. This lowers the melting temperature of mantle rock, generating magma. The magma rises through the crust and feeds volcanoes at the surface.

Over millions of years, repeated volcanic eruptions constructed the Aleutian volcanic arc.

The geometry explains the islands' distinctive curved shape. The Aleutian Trench follows the plate boundary offshore, while the volcanic islands form farther north above the descending Pacific slab. Subduction becomes increasingly oblique toward the western Aleutians, producing changes in volcanism, earthquakes, and crustal deformation along the chain.

Then Ice Began Reshaping the Volcanoes

Building the islands is only half the geological story. Glaciers have repeatedly carved apart the volcanic landscapes created by tectonics.

During colder periods, especially the Pleistocene ice ages, glaciers expanded across parts of the Aleutians. Moving ice eroded volcanic rock, deepened valleys and transported enormous amounts of sediment. When the glaciers retreated, they left behind steep valleys, ridges and deposits that remain visible today.

Modern glacier coverage varies dramatically along the chain. The Aleutians' maritime climate brings abundant moisture, but their relatively low elevations and strong ocean influence make many glaciers particularly sensitive to temperature changes.

Alaska as a whole contains roughly 75,000 square kilometers of glacier ice, although only a fraction lies within the Aleutian chain. The state's glaciers extend all the way west to Kiska Island, demonstrating just how far this glacial environment reaches into the North Pacific.

What Does “Glacial Mass” Actually Mean?

Glacier size isn't determined by temperature alone. Scientists instead examine a glacier's mass balance.

Snowfall adds mass during the accumulation season. Summer melting, evaporation and ice loss remove it. If accumulation exceeds these losses, the glacier gains mass. If melting exceeds accumulation, it loses mass.

Across Alaska, the long-term direction is overwhelmingly toward mass loss. USGS notes that Alaska and western North America currently experience some of the highest glacier-loss rates on Earth.

When Fire and Ice Interact

The Aleutians also demonstrate a less common relationship: glaciers sitting on active volcanic systems.

Geothermal heat can melt ice from underneath, while eruptions can rapidly melt snow and glaciers. The resulting water may become trapped beneath or beside ice before suddenly escaping as a jökulhlaup, or glacial outburst flood. USGS identifies ice-covered Aleutian volcanoes as locations where volcanic and geothermal activity could generate these events.

This makes the Aleutians an unusual geological laboratory. Plate tectonics creates volcanoes, volcanoes build mountains, snowfall creates glaciers, and glaciers erode the volcanoes back down.

The islands we see today are therefore snapshots of a much longer cycle—one in which forces originating hundreds of kilometers inside Earth interact directly with ice sitting only a few kilometers above sea level. 

Antarctica’s Glaciers in 2026

Antarctica contains enough frozen water to raise global sea level by roughly 58 meters if its entire ice sheet melted. Fortunately, such a complete loss is not expected anytime soon. But research published throughout 2026 is revealing something more complicated than a continent simply “melting”: some Antarctic regions are rapidly losing ice while others have temporarily gained mass from unusually heavy snowfall.

The key to understanding this apparent contradiction is ice balance. A glacier gains mass primarily through snowfall and loses it through melting and the movement of ice into the ocean. Antarctica’s overall mass therefore depends on which process is winning.

West Antarctica: The Major Weak Point

Some of the most concerning activity continues to occur in the West Antarctic Ice Sheet, particularly around Pine Island and Thwaites glaciers.

A major 2026 study found that Pine Island Glacier’s retreat has been significantly intensified by human-caused climate change. Researchers estimated that greenhouse-gas-driven warming increased its retreat by about 18–20% since the 1940s, pushing the glacier several kilometers farther inland than it otherwise would have retreated.

The process is driven heavily by the ocean rather than warm air. Relatively warm Circumpolar Deep Water can travel beneath floating ice shelves and melt them from below. When an ice shelf becomes thinner, it provides less resistance against the glacier behind it. That allows grounded ice to accelerate toward the ocean.

This is especially dangerous when a glacier’s grounding line—where ice leaves the bedrock and begins floating—moves inland.

What Scientists Are Finding Beneath Thwaites

Thwaites Glacier remains one of Antarctica’s most closely monitored glaciers. Research published in April 2026 used 344 kilometers of seismic surveys to investigate the landscape hidden beneath its ice.

Scientists discovered a surprisingly complicated environment containing hard rock ridges, sediment-filled basins and widespread subglacial water. Some sediments beneath the glacier are highly porous and saturated with water.

These features matter because glaciers do not simply slide across a smooth rock floor. Hard ridges can resist movement, while water and soft sediment can change friction between the glacier and the ground.

Another 2026 modeling study found that Thwaites’ mass-loss rate has already increased more than fivefold since the 1990s. Some model configurations project losses reaching 180–200 gigatons per year by 2067, although the exact future rate remains uncertain.

But Antarctica Recently Gained Ice?

Surprisingly, yes—temporarily.

Between 2021 and 2023, unusually high snowfall over parts of East Antarctica added enough ice to offset much of the continuing losses elsewhere. New research published in Nature in August 2026 connects much of this snowfall to unusually persistent warming in the tropical Pacific and Indian Ocean region. Changes in atmospheric circulation transported additional moisture toward Antarctica.

Another 2026 study found that increased atmospheric rivers—long corridors carrying concentrated water vapor—have also delivered substantial snowfall to Antarctica.

This does not mean Antarctic melting has reversed. Instead, it shows how complicated ice sheets are. Snowfall can temporarily increase the continent’s total mass even while individual glaciers continue retreating rapidly.

Antarctica Is Really a Giant Flowing System

Perhaps the biggest lesson from 2026 research is that Antarctica should not be imagined as one enormous stationary block of ice.

It is a dynamic system connecting the atmosphere, ocean, glaciers, bedrock and global climate. Satellite observations show that more than three-quarters of Antarctica’s coastal grounding lines have remained relatively stable over the past three decades, while vulnerable regions have retreated dramatically—more than 40 kilometers in some locations.

Understanding those differences will be crucial for predicting sea-level rise. What happens beneath glaciers such as Thwaites and Pine Island today could eventually influence coastlines thousands of kilometers away.

NASAs New Roman Space Telescope

NASA’s Nancy Grace Roman Space Telescope, launched aboard a SpaceX Falcon Heavy in August 2026, represents a different approach to studying the universe. While telescopes such as Hubble and James Webb are famous for extremely detailed observations of relatively small areas, Roman is designed to combine sharp imaging with a huge field of view. The result will be enormous maps that allow scientists to study how galaxies, matter, and even the expansion of the universe have changed over cosmic time.

At the center of Roman is a 2.4-meter-wide primary mirror, roughly the same diameter as Hubble’s. Its Wide Field Instrument, however, can capture an area of sky about 100 times larger than Hubble can in a single exposure. This means Roman can observe millions of objects while maintaining the resolution necessary to distinguish distant galaxies and stars.

Mapping the Invisible Universe

One of Roman’s most important scientific targets is something telescopes cannot directly photograph: dark matter.

Dark matter does not emit or reflect light, but its gravity affects ordinary matter and bends light traveling through space. Roman will exploit a phenomenon called gravitational lensing, in which the gravity of massive objects slightly distorts the appearance of galaxies behind them.

By measuring millions of these tiny distortions, scientists can reconstruct maps showing where otherwise invisible dark matter is concentrated. Comparing those maps across different distances—and therefore different periods of cosmic history—could reveal how the universe’s large-scale structure developed.

Roman will also investigate dark energy, the name given to whatever is driving the accelerating expansion of the universe. By measuring galaxy distributions and exploding stars called Type Ia supernovae, astronomers can reconstruct how quickly the universe expanded at different points in its history.

Turning the Milky Way Into a Planet Survey

Roman will also use an interesting gravitational effect to discover planets. Gravitational microlensing occurs when a foreground star passes almost perfectly in front of a more distant star. The foreground star’s gravity bends and magnifies the background star’s light.

If a planet orbits the foreground star, its gravity can create an additional temporary change in brightness.

This technique allows Roman to detect worlds that are difficult to find with traditional exoplanet searches, including planets located relatively far from their stars and potentially even free-floating planets traveling through the galaxy without a host star.

Testing Technology for Finding Another Earth

Roman also carries a Coronagraph Instrument, which demonstrates technology for directly observing planets around other stars. Stars can be billions of times brighter than their planets, making an exoplanet somewhat like trying to photograph a firefly beside a searchlight.

A coronagraph blocks much of the star’s light while allowing nearby planetary light to reach the telescope. Roman’s instrument is primarily a technology demonstration, but what engineers learn from it could contribute to future observatories designed to directly image Earth-like planets.

From Individual Galaxies to the Cosmic Web

Perhaps Roman’s greatest scientific advantage is scale. Webb can examine individual galaxies with extraordinary sensitivity; Roman can examine enormous populations of galaxies simultaneously.

Those observations should reveal the cosmic web—the immense network of galaxy clusters, filaments, and empty voids created as gravity shaped matter over billions of years.

Roman therefore isn’t simply another telescope producing beautiful images. It is essentially a cosmic mapping machine. By combining gravitational physics, infrared astronomy, exoplanet science, and massive surveys, Roman could help connect some of astronomy’s biggest questions: how planets form, how galaxies evolve, where invisible matter is located, and ultimately, why the universe looks the way it does today.

Nepal’s 2026 Flood Crisis

On August 26, 2026, communities along Nepal’s Himalayan river valleys were struck by one of the country’s most destructive recent natural disasters. A sudden torrent of water, mud, boulders, and ice rushed through the Lhende Khola–Bhote Koshi–Trishuli river system, devastating settlements in Rasuwa before continuing downstream through Nuwakot, Dhading, and other districts.

Unlike many of Nepal’s floods, this disaster was not primarily caused by heavy monsoon rainfall. Scientists now believe it began thousands of meters above the affected communities when a huge section of Himalayan glacier, along with rock beneath it, suddenly collapsed. The resulting ice-rock avalanche plunged into the Lhende Khola valley, picking up enormous quantities of sediment and debris.

From Glacier Collapse to Flash Flood

The collapse appears to have temporarily blocked the Lhende River, essentially creating a short-lived natural dam. Water accumulated behind the debris until the blockage failed. The sudden release transformed the river into a fast-moving debris flood carrying water, mud, rocks, trees, and pieces of infrastructure downstream. Scientists are still investigating exactly how the blockage formed and whether nearby glacial water contributed to the flood.

The speed of the event made it especially dangerous. River levels reportedly increased by as much as nine meters—nearly 30 feet—in only 30 minutes. Roads, bridges, buildings, hydropower facilities, and entire communities were caught in the flood path.

Why Did the Glacier Collapse?

Climate change is an important part of the larger story. The Hindu Kush Himalaya is warming rapidly, causing glaciers to retreat and changing the stability of high mountain slopes. Melting ice can remove support from surrounding rock, while thawing permafrost can weaken material that previously remained frozen together. These processes can increase the potential for rockfalls, ice avalanches, landslides, and sudden floods.

Scientists are careful not to say that warming alone caused this particular collapse—the exact trigger remains under investigation. However, the disaster demonstrates how climate change can create conditions in which Himalayan landscapes become increasingly unstable.

A Growing Himalayan Hazard

Nepal’s geography makes the country particularly vulnerable. Steep mountains channel floodwaters into narrow valleys where communities, highways, bridges, and hydropower projects are often concentrated. Once an avalanche or landslide enters a river, the effects can therefore travel far beyond the original collapse.

The August disaster is consequently more than a story about flooding. It demonstrates a chain reaction: warming climate → glacier and mountain instability → ice-rock avalanche → river blockage → dam failure → catastrophic downstream flooding.

As Himalayan glaciers continue changing, better satellite monitoring, river gauges, cross-border data sharing, hazard mapping, and early-warning systems will become increasingly important. Nepal’s latest disaster shows that understanding glaciers is no longer only about measuring ice loss—it can also be a matter of protecting communities hundreds of kilometers downstream.

Permafrost and Ice Quakes

Across the coldest regions of Earth, frozen ground and massive sheets of ice create landscapes unlike anywhere else on the planet. In places such as the Arctic, Antarctica, Alaska, Canada, and Siberia, temperatures remain low enough for soil and water to freeze for long periods of time. Two fascinating features of these frozen environments are permafrost and ice quakes, which reveal the powerful forces constantly shaping polar and high-latitude regions.

Permafrost is ground that remains frozen for at least two consecutive years. It is made up of soil, rock, sand, and ice that stay below freezing temperatures for long periods. Permafrost covers large areas of the Northern Hemisphere, especially across Alaska, Canada, Greenland, and Russia. In some regions, it can extend hundreds of meters beneath Earth’s surface.

Although permafrost may seem like solid, permanent ground, it is actually a dynamic system. The upper layer, known as the active layer, freezes during winter and thaws during the warmer months. Plants, animals, and microorganisms live within this thin surface zone. Beneath it, the deeper permafrost remains frozen year-round, preserving ancient organic material that has been trapped for thousands of years.

Permafrost plays an important role in global climate regulation. Frozen soils store enormous amounts of carbon that accumulated from plants and organisms over thousands of years. When permafrost thaws, microorganisms can break down this organic material, releasing greenhouse gases such as carbon dioxide and methane into the atmosphere. These gases contribute to warming, creating a feedback cycle where rising temperatures cause more thawing, which can lead to additional warming.

As permafrost changes, the ground can become unstable. Buildings, roads, pipelines, and other infrastructure in Arctic regions may be affected as frozen ground loses its strength and begins to settle. Scientists monitor permafrost temperatures and changes to understand how these landscapes are responding to a warming climate.

Another dramatic phenomenon in frozen environments is the ice quake, also known as a cryoseism. Ice quakes are sudden cracking events caused by the rapid freezing and expansion of water within frozen ground or glaciers. Unlike earthquakes, which occur due to movement of Earth’s tectonic plates, ice quakes are driven by changes in temperature and pressure within ice and frozen soil.

Ice quakes can occur when water trapped in the ground freezes quickly and expands, creating pressure that fractures the surrounding material. They can also happen within glaciers when large sections of ice shift, crack, or adjust due to stress. These events can produce loud booming sounds and vibrations that may be detected by sensitive instruments.

Scientists study ice quakes because they provide valuable information about changes occurring in frozen landscapes. Monitoring these events helps researchers understand glacier movement, ice sheet behavior, and the effects of changing temperatures in polar environments.

Permafrost and ice quakes demonstrate that frozen landscapes are not motionless or lifeless. Beneath the snow and ice, powerful natural processes are constantly occurring. As climate conditions continue to change, understanding these frozen systems becomes increasingly important for predicting future environmental changes and protecting communities that depend on stable Arctic landscapes.

From ancient frozen soils storing carbon to glaciers cracking under pressure, the hidden world of ice reveals the complex and ever-changing nature of Earth’s coldest regions.

Exploring Places Below Sea Level

When most people think about Earth’s surface, they imagine land rising above the ocean. However, several remarkable places around the world lie below sea level, meaning their elevation is lower than the average level of the world’s oceans. These unique landscapes were formed through a combination of tectonic activity, erosion, evaporation, and human engineering. Despite their unusual elevations, many of these regions support thriving ecosystems, agriculture, tourism, and even permanent communities.

One of the best-known places below sea level is the Dead Sea, located between Jordan and Israel and the West Bank. Its shoreline sits more than 430 meters (1,410 feet) below sea level, making it the lowest exposed land on Earth. Because the lake has no outlet, water evaporates quickly, leaving behind extremely high concentrations of salt. This high salinity allows people to float effortlessly and supports only specialized microorganisms rather than fish or aquatic plants.

Another famous example is Death Valley in California, home to Badwater Basin, the lowest point in North America at approximately 86 meters (282 feet) below sea level. Death Valley formed as the Earth’s crust stretched and dropped along fault lines. The region experiences some of the hottest temperatures ever recorded and receives very little rainfall. Salt flats cover much of the basin, creating a striking white landscape against the surrounding mountains.

The Danakil Depression in Ethiopia is another extraordinary below-sea-level region. Formed where tectonic plates are slowly pulling apart, it contains colorful mineral deposits, active volcanic areas, hot springs, and salt flats. Extreme heat and geothermal activity make it one of the harshest environments on the planet, yet it remains an important site for geological research.

Not all below-sea-level regions are natural. Large parts of the Netherlands lie below sea level because of centuries of land reclamation. Through the construction of dikes, canals, pumps, and polders, the Dutch have successfully protected communities and farmland from flooding. Today, millions of people live safely in these engineered landscapes, demonstrating how technology and careful planning can overcome challenging geography.

Areas below sea level often face unique environmental concerns. Rising sea levels caused by climate change increase the risk of flooding in low-lying regions, particularly those protected by levees and dikes. In inland basins such as the Dead Sea, declining water levels caused by reduced river inflow and evaporation continue to reshape the landscape. Scientists closely monitor these areas to better understand how natural processes and human activities affect them.

From the salt-covered plains of Death Valley to the floating waters of the Dead Sea and the engineered polders of the Netherlands, below-sea-level landscapes showcase Earth’s incredible geological diversity. These remarkable regions remind us that elevation alone does not determine whether a place can support life, attract visitors, or play an important role in understanding our dynamic planet.

Chamonix and Its Alpine Glaciers

Nestled in the French Alps at the foot of Mont Blanc, Chamonix is one of the world’s most famous mountain destinations. Known for its breathtaking scenery, mountaineering history, and year-round outdoor recreation, the town attracts millions of visitors each year. Surrounded by towering peaks and expansive glaciers, Chamonix offers a unique opportunity to experience some of Europe’s most impressive alpine landscapes while learning about the power and beauty of moving ice.

The most famous glacier in the Chamonix Valley is the Mer de Glace, or “Sea of Ice.” Stretching about 7 kilometers (4.3 miles), it is the largest glacier in France. The glacier originates high on the slopes of the Mont Blanc massif, where snowfall accumulates and gradually compresses into dense glacial ice. Over time, gravity causes this ice to flow slowly downhill, carving valleys and transporting rock and sediment. Although the glacier appears motionless, it is constantly moving, reshaping the landscape over thousands of years.

Visitors can reach the Mer de Glace by riding the historic Montenvers Railway, which climbs from Chamonix to an overlook with stunning panoramic views. From there, guests can descend to explore an ice cave carved into the glacier each year. Inside, shimmering blue walls and frozen tunnels provide an unforgettable glimpse into the interior of a living glacier, helping visitors appreciate how these massive rivers of ice are constantly changing.

Another iconic attraction is the Aiguille du Midi, a towering peak accessible by one of the world’s highest cable cars. At an elevation of 3,842 meters (12,605 feet), visitors are rewarded with spectacular views of the Mont Blanc massif and the surrounding glaciers. From this vantage point, the scale of the alpine icefields becomes clear, highlighting the close relationship between the mountains, glaciers, and valleys below.

Like many glaciers around the world, those in the Chamonix Valley have been retreating due to rising temperatures and changing snowfall patterns. Scientists have documented significant ice loss at the Mer de Glace over the past century, and markers along the hiking trails show where the glacier once reached decades ago. These visible changes provide powerful evidence of how climate influences mountain environments and water resources.

Despite these challenges, Chamonix remains an important center for scientific research, environmental education, and outdoor adventure. Hikers, climbers, skiers, and researchers all come to experience the remarkable alpine landscape while studying its ongoing transformation.

Whether viewed from a mountain summit, explored through an ice cave, or admired from the valley below, the glaciers of Chamonix showcase both the beauty and fragility of Earth’s frozen environments. They remind us that glaciers are not only spectacular natural wonders but also valuable indicators of our planet’s changing climate.

What are Nunataks?

In some of the world’s most heavily glaciated landscapes, rocky mountain peaks can be seen rising dramatically above vast sheets of ice. These exposed summits are called nunataks, a word that comes from the Inuit language and means “lonely peak.” Found in places such as Greenland, Antarctica, Alaska, the Canadian Arctic, and high mountain ranges, nunataks provide a fascinating glimpse into the interaction between glaciers and mountains.

A nunatak forms when a glacier or ice sheet grows thick enough to cover most of a mountain, but not its highest summit. As snow accumulates over many years, it compresses into dense glacial ice that slowly flows downhill under its own weight. If the surrounding ice becomes deep enough, only the tallest portions of the mountain remain exposed above the glacier. These rocky peaks stand like islands in a frozen sea, surrounded by moving ice on all sides.

Nunataks can also become more visible as glaciers retreat. Rising global temperatures and changing snowfall patterns have caused many glaciers to shrink over the past century. As the ice melts away, more of the mountain is exposed, and areas that were once isolated above the glacier become connected to the surrounding landscape. Scientists study these newly exposed rocks to learn about past glacial conditions and how Earth’s climate has changed over time.

Although nunataks appear harsh and lifeless, they often support unique ecosystems. Because they remain free of permanent ice, hardy plants such as mosses, lichens, and small alpine flowers can grow in cracks within the rock. These plants provide food and shelter for insects and birds, making nunataks important refuges for life in otherwise icy environments. During past ice ages, some species may have survived on nunataks while surrounding areas remained buried beneath thick glaciers.

Nunataks are also valuable to scientists studying glaciers and climate. Since the rocks are exposed to the atmosphere, researchers can analyze their surfaces using techniques such as cosmogenic exposure dating to determine how long they have been free of ice. This information helps reconstruct the history of glacier advance and retreat and improves our understanding of how ice sheets respond to changes in climate.

Many famous mountain landscapes contain nunataks. In Antarctica and Greenland, countless rocky peaks rise above immense ice sheets, creating spectacular scenery. Similar features can also be found in glaciated regions of the Alps, Alaska, and even around Mount Rainier, where volcanic ridges and peaks sometimes protrude above surrounding glaciers.

Nunataks are striking reminders of the power of glaciers to shape Earth’s surface. These isolated peaks reveal both the immense thickness of ancient ice and the resilience of life in extreme environments, making them one of the most fascinating landforms found in glaciated regions.