Active Volcanoes to Watch

Volcanoes are among the most dynamic features of Earth’s surface, capable of reshaping landscapes and impacting global systems within days. While predicting exact eruption times remains challenging, scientists can identify volcanoes that are highly likely to erupt within this century based on historical activity, geodetic measurements, and magma system behavior. These “high-risk” volcanoes are closely monitored using modern tools to better understand when and how they may erupt.

One of the most active volcanoes in the world is Mount Etna in Italy. Etna erupts frequently, often producing lava flows and ash plumes that can disrupt air travel and nearby communities. Its consistent activity makes it a key site for studying magma movement and eruption cycles. Similarly, Mount St. Helens in the United States remains an important volcano to watch. Since its catastrophic 1980 eruption, it has shown periodic dome-building activity, indicating that its magma system is still active.

In Indonesia, several volcanoes are considered among the most dangerous due to both their activity and nearby population density. Mount Merapi is one of the most closely monitored volcanoes in the world, erupting regularly and posing significant risk to surrounding communities. Its eruptions are often explosive, generating pyroclastic flows that can travel at high speeds. The combination of frequent activity and dense populations makes Merapi a critical focus for volcanic hazard mitigation.

Another major system is Campi Flegrei, a large volcanic caldera near Naples. Unlike typical cone-shaped volcanoes, Campi Flegrei is a vast, underground system that has shown signs of unrest, including ground uplift and increased gas emissions. These changes are detected through geodetic tools such as GNSS and InSAR, which measure subtle surface deformation. Although it has not erupted since 1538, its recent activity suggests a heightened likelihood of future eruptions within this century.

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Perhaps the most widely discussed volcanic system is Yellowstone Caldera in the United States. While often labeled a “supervolcano,” a massive eruption is considered unlikely in the near future. However, Yellowstone experiences frequent seismic activity and ground deformation, indicating an active magma system. Smaller hydrothermal or lava flow events are more probable and are continuously monitored by scientists.

In Mexico, Popocatépetl has been highly active in recent decades, producing frequent ash emissions and minor eruptions. Its proximity to large urban centers makes it one of the most closely watched volcanoes in North America. Continuous monitoring helps provide early warnings and reduce risks to nearby populations.

Modern geodesy plays a crucial role in forecasting volcanic activity. Techniques such as GNSS measure ground deformation caused by magma movement beneath the surface, while InSAR provides satellite-based observations of surface changes over time. Gas emissions, seismic activity, and thermal imaging are also integrated into monitoring systems. Together, these tools allow scientists to detect early signs of unrest, even if precise eruption timing remains uncertain.

It is important to note that “due to erupt” does not mean an eruption is imminent, but rather that these volcanoes have a high probability of activity based on past behavior and current signals. Volcanoes operate on complex timescales, and even well-monitored systems can remain quiet for decades before erupting.

In conclusion, while we cannot predict exactly when a volcano will erupt, we can identify which systems are most likely to become active in the coming decades. Continuous monitoring and advances in geodesy are improving our ability to understand these powerful natural processes, helping societies better prepare for future eruptions.

Are Glaciers Endangered?

Glaciers—slow-moving rivers of ice that have shaped Earth’s landscapes for thousands of years—are increasingly considered one of the most vulnerable components of the cryosphere. The question “Are glaciers endangered?” is no longer hypothetical. Across the globe, observational data shows that most glaciers are retreating, thinning, and losing mass at accelerating rates, raising concerns about long-term environmental and societal impacts.

A glacier forms when snowfall accumulates over time, compressing into dense ice that flows under its own weight. This system depends on a delicate balance between accumulation (snowfall) and ablation (melting, sublimation, and calving). When this balance is disrupted—primarily by rising global temperatures—glaciers begin to shrink. Today, this imbalance is widespread, driven largely by anthropogenic climate change.

Regions such as Alaska, Greenland, and the Himalayas are experiencing some of the most dramatic changes. Satellite observations and field measurements show consistent negative mass balance, meaning glaciers are losing more ice than they gain each year. In Greenland, surface meltwater rivers now carve across the ice sheet during summer months, accelerating ice flow toward the ocean. In the Himalayas, often referred to as the “Third Pole,” glacier retreat threatens freshwater supplies for millions of people downstream.

From a geodetic standpoint, glacier loss has measurable effects on Earth’s surface. As ice mass decreases, the underlying crust experiences uplift through a process known as glacial isostatic adjustment (GIA). Instruments such as GNSS stations detect millimeter-scale vertical motion, while satellite gravimetry tracks changes in mass distribution. These measurements confirm that glacier loss is not only visible but also quantifiable at high precision.

The implications of endangered glaciers extend far beyond mountainous regions. One of the most significant consequences is global sea-level rise. When land-based ice melts, it contributes directly to increasing ocean volume. Satellite altimetry has shown a steady rise in global mean sea level over recent decades, with glacier melt being a major contributor alongside thermal expansion of seawater. Even small glaciers, when considered collectively, play a substantial role in this process.

In addition to sea-level rise, glacier retreat affects freshwater availability, ecosystems, and natural hazards. Many river systems depend on seasonal glacier melt to sustain flow during dry periods. As glaciers shrink, this natural regulation weakens, leading to water shortages in some regions and increased flood risk in others. The formation of unstable glacial lakes can also result in sudden outburst floods, posing risks to nearby communities.

However, not all glaciers are disappearing at the same rate. Some, like Perito Moreno Glacier in Patagonia, remain relatively stable due to unique local conditions. These exceptions highlight the complexity of glacier systems, where factors such as topography, precipitation, and temperature interact in different ways. Still, these stable glaciers are the minority in a global trend of decline.

So, are glaciers endangered? The evidence strongly suggests yes—most glaciers are in a state of rapid change and long-term retreat. While complete disappearance may take decades or centuries for some, the current trajectory indicates significant loss within human timescales. This makes glaciers not only endangered natural features but also critical indicators of climate change.

In conclusion, glaciers are more than frozen landscapes; they are essential components of Earth’s environmental system. Their decline signals broader shifts in climate, water resources, and sea levels. Continued monitoring through geodesy and remote sensing will be vital in understanding their future—and in determining how humanity responds to their loss.

How are Glaciers and Ice Sheets Created?

Glaciers and ice sheets are both formed from snow, but the conditions required to create them—and the scales at which they exist—are very different. Understanding how each forms reveals why glaciers can appear in mountainous regions around the world, while ice sheets exist only in a few extreme environments on Earth.

The Creation of a Glacier

A glacier begins with persistent snowfall. For a glacier to form, more snow must fall in a given area each year than melts away during warmer seasons. This typically occurs at high elevations or high latitudes where temperatures remain low enough for snow to survive year-round.

Over time, layers of snow accumulate. The weight of new snowfall compresses the older snow beneath it, squeezing out air and transforming the snow into a dense, granular material called firn. With continued burial and pressure, firn recrystallizes into solid glacial ice. This process can take decades to centuries, depending on temperature and snowfall rates.

Once the ice becomes thick enough—generally tens of meters—it begins to flow under its own weight. Gravity drives the ice downhill, allowing it to move slowly across the landscape. At this point, the mass of ice is officially a glacier. Valley glaciers follow existing terrain such as mountain valleys, while cirque glaciers form in bowl-shaped depressions near mountain peaks.

Glaciers are highly sensitive to climate. Small changes in temperature or precipitation can determine whether a glacier grows, remains stable, or retreats. This is why glaciers are found across a wide range of environments, from the Andes and Himalayas to Alaska and New Zealand.

The Creation of an Ice Sheet

Ice sheets form through the same basic process—snow accumulation, compaction, and ice flow—but at a vastly larger scale. An ice sheet requires not just cold temperatures, but an entire region cold enough year-round to prevent widespread melting.

Unlike glaciers, ice sheets are not confined by valleys or topography. Instead, they become so thick—often several kilometers—that they override the underlying landscape, flowing outward in all directions from a central high point. Gravity causes the ice to spread laterally, creating a continent-scale body of moving ice.

Today, Earth has only two ice sheets: one in Antarctica and one in Greenland. These ice sheets formed over hundreds of thousands to millions of years during periods of sustained global cooling. Antarctica’s ice sheet alone contains enough frozen water to raise global sea levels by nearly 60 meters if fully melted.

Ice sheets require a delicate balance: extremely cold air temperatures, sufficient snowfall to sustain growth, and minimal summer melting. Once established, they strongly influence regional and global climate by reflecting sunlight (the albedo effect) and shaping atmospheric circulation.

Key Differences in Formation

The most important distinction between glacier and ice sheet formation is scale and persistence. Glaciers can form relatively quickly in favorable climates and disappear just as quickly when conditions change. Ice sheets, by contrast, are products of long-term planetary cooling and are far more stable—though modern warming is now pushing even these massive systems toward retreat.

Another difference lies in topographic control. Glaciers are shaped by the land beneath them, while ice sheets reshape the land itself. Ice sheets generate outlet glaciers that behave like conventional glaciers at their margins, but their origins remain fundamentally continental.

Why This Difference Matters

Understanding how glaciers and ice sheets form helps scientists predict how they will respond to climate change. Glaciers act as early warning signals, responding rapidly to warming. Ice sheets respond more slowly, but their potential impact on sea level is far greater.

Both begin as simple snowfall—but whether that snow becomes a glacier or an ice sheet depends on time, temperature, and scale. Together, they represent different expressions of the same powerful process: the transformation of snow into flowing ice that reshapes Earth’s surface.

Post Number 100!

I would like to thank each and every one of you for joining me on this blogging journey for over a year and through 100 posts! What started as a small idea to share updates about satellites, GNSS, and gravity has grown into a global conversation about how we measure and understand our planet. Along the way,  everything from shifting tectonic plates to sea-level rise and the incredible precision of atomic clocks has been covered. I have had a lot of fun and learned a lot while doing this, so here's to many more posts in the future! Please contact me with any questions or concerns regarding any of the content on this website! I look forward to hearing from you all :)

The Ice Ages

Earth’s climate has shifted dramatically over the millennia, swinging between warmer interglacial times and colder glacial periods. During these colder epochs, massive ice sheets advanced over continents, reshaping landscapes, ecosystems, and even human migration. Among the most well-known glacial periods are the Wisconsinan in North America, but several others across the globe left equally profound marks.

The Wisconsinan Glaciation (North America)

The Wisconsinan glaciation, the most recent advance of the Laurentide Ice Sheet, began around 85,000 years ago and ended roughly 11,000 years ago. It defined much of the landscape we see in the northern United States and Canada today. Thick ice sheets carved out the Great Lakes, deposited fertile soils across the Midwest, and left behind glacial features like moraines and eskers. For humans, the Wisconsinan coincided with the spread of early Paleo-Indians into the Americas, who had to adapt to harsh, cold conditions.

The Weichselian Glaciation (Europe)

Parallel to the Wisconsinan was the Weichselian glaciation in northern Europe. Stretching across Scandinavia and into Germany and Poland, the ice carved deep fjords and left vast plains behind when it retreated. The Weichselian also influenced human history—many early hunter-gatherer groups in Europe migrated southward into more hospitable areas, setting the stage for later resettlement as the ice retreated.

The Devensian Glaciation (British Isles)

In Britain, the Devensian glaciation covered large parts of Scotland, Ireland, and northern England. This ice sculpted U-shaped valleys in the Scottish Highlands and deposited boulder-strewn landscapes still visible today. Much like elsewhere, the ice forced human and animal populations to the southern coasts and shaped the island’s long-term geography.

Older Glacial Periods

Beyond the last Ice Age, earlier glacial episodes reveal how repeatedly Earth has been transformed. The Illinoian glaciation (before the Wisconsinan) reached farther south than later ice sheets, even into present-day Kentucky. The Kansan and Nebraskan glaciations, dating back over 600,000 years, mark some of the earliest recognized ice advances in North America. Globally, the Saalian in Europe and the Mindel and Riss glaciations in the Alps left their imprint on valleys, rivers, and mountains.

What These Glacial Periods Were Known For

- Landform creation: Glaciers carved valleys, lakes, and fertile plains that became crucial for farming and settlement.

- Climate shifts: Alternating cold glacial and warm interglacial cycles shaped biodiversity, driving some species to extinction while allowing others to thrive.

- Human migration: Ice ages pushed human groups into new territories, influencing cultural development and survival strategies.

Why They Matter Today

Understanding glacial periods is more than studying frozen history. These cycles reveal Earth’s sensitivity to climate change and natural feedback systems. As modern warming accelerates, lessons from past ice ages help scientists anticipate how today’s climate shifts might reshape coasts, ecosystems, and societies in the centuries ahead.

Most Researched Geodesy Topics

Geodesy, often called the “science of measurement,” underpins our understanding of the Earth’s shape, gravity field, and dynamics. As technology evolves and environmental challenges mount, geodesy continues to expand its boundaries—from deep space to deep Earth. In recent years, several research themes have emerged as particularly active and influential within the global geodesy community.

1. Reference Frames and Earth Rotation

Defining and maintaining global reference frames remains one of geodesy’s most critical and continuously researched areas. The International Terrestrial Reference Frame (ITRF) and its updates rely on integrated observations from GNSS, VLBI, SLR, and DORIS systems. Research focuses on improving frame stability, accounting for tectonic motion, post-glacial rebound, and even the impact of climate-induced mass redistribution. Closely tied to this is the study of Earth rotation and orientation parameters, which link terrestrial and celestial coordinate systems and reveal subtle variations driven by mass movement within the oceans, atmosphere, and core.

2. Gravity Field and Mass Transport

The Earth’s gravity field remains a vibrant research frontier. Satellite missions such as GRACE, GRACE-FO, and GOCE have revolutionized how scientists monitor mass changes over time. Current studies explore gravity-based insights into melting ice sheets, groundwater depletion, and glacial isostatic adjustment. Researchers are developing new models that merge satellite gravimetry, terrestrial gravity data, and ocean altimetry to refine temporal resolution and reduce uncertainty in mass redistribution estimates—key for understanding sea-level rise and climate change.

3. GNSS Modernization and Multi-GNSS Integration

Global Navigation Satellite Systems (GPS, Galileo, GLONASS, BeiDou, and NavIC) are the backbone of modern geodesy. Current research explores integrating multiple constellations for enhanced accuracy, resilience, and timing precision. Multi-GNSS methods are also being combined with real-time processing to improve positioning for earthquake monitoring, infrastructure stability, and rapid disaster response. Innovations in antenna design, atmospheric correction modeling, and ionospheric delay estimation continue to push GNSS geodesy into higher precision realms.

4. Satellite Altimetry and Sea-Level Research

Sea-level monitoring through radar altimetry has become one of geodesy’s most interdisciplinary topics, linking climate, oceanography, and hydrology. The Sentinel-6 and SWOT missions are producing unprecedented coastal and inland water data, while scientists refine sea-surface height models to correct for tides, geoid variations, and atmospheric interference. Research also focuses on closing the “sea-level budget” by connecting observations from altimetry, gravimetry, and in situ sensors.

5. Deformation and Geohazards

Crustal deformation monitoring using InSAR and GNSS arrays remains central to understanding earthquakes, volcanic activity, and land subsidence. Recent work emphasizes near-real-time deformation modeling for early warning systems. Machine learning is increasingly used to detect subtle deformation signals in noisy datasets, improving prediction and risk assessment for tectonically active regions.

6. Emerging Field: Chronometric Geodesy

A cutting-edge frontier is chronometric geodesy—using ultra-precise optical atomic clocks to measure gravity potential differences directly. This approach could redefine height systems and provide new tools for geoid determination. As global clock networks expand, researchers foresee integrating time-based geodesy into the broader terrestrial reference system by the 2030s.

Conclusion

Geodesy today sits at the intersection of measurement science, climate research, and data technology. The most researched topics—reference frames, gravity, GNSS integration, altimetry, deformation, and chronometric geodesy—all share a common aim: improving how humanity observes and understands a dynamic Earth. As satellites grow more precise and algorithms more intelligent, the field continues to evolve from static measurement to living observation—capturing our planet in motion with ever greater clarity. 

Leading Institutions for Glacier Research

As climate change accelerates and its effects become more evident, understanding glaciers has never been more urgent. Glaciers are not just frozen rivers of ice; they’re vital indicators of Earth’s climate health, critical freshwater reservoirs, and key players in sea-level change. Around the globe, a handful of institutions stand out as leaders in glaciology research—shaping global climate models, advancing satellite observation, and influencing environmental policy. Here are the top institutions driving glacier science forward:

1. University of Alaska Fairbanks (UAF) – Geophysical Institute

Located in the heart of glacial Alaska, UAF is a powerhouse in Arctic and sub-Arctic research. Its Geophysical Institute, through the Snow, Ice and Permafrost Group, leads cutting-edge work on glacier dynamics, mass balance monitoring, and remote sensing. Researchers at UAF frequently publish on the retreat of Alaskan glaciers and their contributions to global sea level rise.

2. Swiss Federal Institute for Forest, Snow and Landscape Research (WSL)

Switzerland is home to some of the most advanced glacier monitoring networks in the world, and WSL plays a central role. Its Cryospheric Sciences division collaborates with ETH Zurich to model glacier evolution in the Alps and globally. WSL scientists also operate long-term glacier mass balance studies that are among the most comprehensive in Europe.

3. Norwegian Polar Institute (NPI)

Specializing in Arctic glaciology, NPI conducts fieldwork in Svalbard and Antarctica. Their work is essential in understanding the behavior of marine-terminating glaciers and their role in polar sea-level contributions. NPI also contributes to IPCC reports and Arctic policy frameworks.

4. British Antarctic Survey (BAS)

Based in Cambridge, UK, BAS is a world leader in Antarctic glacier research. Their teams use aircraft-mounted radar, satellites, and ice core drilling to study ice shelves, basal melting, and ice sheet stability. BAS research is key in forecasting Antarctic contributions to future sea-level rise.

5. National Snow and Ice Data Center (NSIDC), University of Colorado Boulder

NSIDC is a global hub for cryospheric data. It provides crucial satellite data on ice mass loss, glacier extent, and snow cover. The center supports NASA missions like ICESat and Operation IceBridge, enabling better global glacier monitoring.

Honorable Mentions:

- Institute of Arctic and Alpine Research (INSTAAR), Colorado

- Centre for Ice and Climate, University of Copenhagen

- Alfred Wegener Institute, Germany

- Indian Institute of Science (IISc), Bangalore – increasingly active in Himalayan glacier studies

These institutions not only advance scientific understanding but also inform climate adaptation efforts worldwide. Their work ensures that humanity stays informed on one of Earth’s most dynamic and vulnerable systems—our glaciers.

What Even Is Geodesy?

Geodesy is a field of earth science that looks at measuring the changes in Earth's geometric shape, as a result of various factors like glacial movement, tectonic activity, and human impacts. This field combines math, physics, and astronomy to understand Earth's properties.

Some key aspects of this field are:

- Earth's Shape: Geodesists measure and analyze the Earth's shape (geoid) and size. The geoid is the hypothetical sea level surface around the Earth, which represents the global mean sea level without ocean currents, waves, and tides.

- Navigation: Geodesy provides the basis for positioning and navigation systems, such as GPS (Global Positioning System). Accurate geodetic measurements are crucial for mapping and satellite navigation.

- Time Changes: The discipline also looks at how the Earth's shape and gravitational field change over time due to various factors like tectonic activity, glacial melting, and sea level rise.

- Applications: Geodesy has applications in various fields, including surveying, mapping, navigation, oceanography, and environmental studies. It is also key to understanding and mitigating natural hazards such as earthquakes and tsunamis.

Intro

Hi! I'm Sarayu, a rising high school junior at Okemos High School interested in geodesy. I wanted to document my journey and findings :) I became interested in this field after I joined a club in fifth grade called Science Olympiad. I competed in an event called Dynamic Planet, where we learned about natural sciences. I am currently participating in my seventh year of Science Olympiad, and this interest drove me to join a class in my school called Science Research Seminar. Here, I got an opportunity to further explore my interest in the natural sciences and found earth sciences to be what I wanted to narrow in on. I read a lot of research articles, and am excited to learn more!