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TABLE OF CONTENTS
- Crystal Structure-
- Density-
- Neve-
- Firn-
- Ablation-
- Equilibrium line-
- Basal sliding-
- Valley/Alpine Glaciers-
- Cirque-
- Hanging-
- Piedmont-
- Ice sheet/continental-
- Ice Stream-
- Ice Shelf-
- Ice Cap-
- Ice Tongue-
- Features of Glacial Ice-
- Crevasses-
- Ogives-
- Ice Falls-
- Calving-
- Marine Ice Shelf Instability-
- Ice Shelf Buttressing-
- Landscape features by:
- Erosion:
- Hanging valley-
- Aretes-
- Horns-
- Striation-
- Roche Mountonnee-
- Depositional-
- Terminal Moraines-
- Recessional Moraine-
- Lateral Moraine-
- Medial Moraine-
- Ground Moraine-
- Kames-
- Drumlins-
- Esker-
- Erratic-
- Lakes-
- Tarns-
- Great Lakes-
- Finger Lakes-
- Kettle-
- Moraine-dammed lake-
- Proglacial Lakes-
- Periglacial Processes-
- Sea Ice-
- Ice Floe-
- Draft vs. Freeboard-
- Pressure Ridge-
- Frazil Ice-
- Pancake Ice-
- Glacial Hydrology-
- Surface melt-
- Moulin-
- Drainage-
- Subglacial lakes-
- Atmosphere-
- Amplified melting due to changes in albedo-
- Release of gases from glacial melting-
- Oceans-
- Sea level change and ice sheet variation-
- Lithosphere-
- Isostatic effects on earth’s crust-
- History of Ice on earth-
- Drop Stones-
- Striations-
- Sedimentary deposits-
- Neoproterozoic Era-
- Late Paleozoic ice ages-
- passage- Eocene oligocene transition and the impact of opening oceanic seaways such as the drake
- Larsen B.-
- Laurentide Ice Sheet-
- Thwaites Glacier-
Depth variations: The density of glacier ice can vary depending on the depth within the glacier, with deeper layers potentially being denser due to increased pressure;.
Neve-
young, granular snow that has been partially melted, refrozen and compacted
Firn-
Firn is usually defined as snow that is at least one year old and has therefore survived one melt season, without being transformed to glacier ice. Firn is transformed gradually to glacier ice as density increases with depth, as older snow is buried by newer snow falling on top of it.
Ablation-
combined processes (such as sublimation, fusion or melting, evaporation) which remove snow or ice from the surface of a glacier or from a snow-field
Equilibrium line-
The zone where there is net accumulation (where there is more mass gained than lost) is the accumulation zone. The part of the glacier that has more ablation than accumulation is the ablation zone. Where ablation is equal to accumulation is the Equilibrium line altitude.
Basal sliding-
Glaciers can slide because ice melts under pressure, resulting in a film of water at the ice-bed interface. This can facilitate decoupling and enhance fast ice flow. If the glacier bed is rough, with many bumps and obstacles, this increases melting and ice flow. This process is known as regelation. If water pressures become high enough, cavities can form at the ice-bed interface, causing sliding with bed separation. This reduces basal friction and allows faster ice flow. Sliding velocity is controlled by basal shear stress and effective pressure, which is the difference
between ice overburden pressure and water pressure (Jiskoot et al., 2011).
Valley/Alpine Glaciers-
Cirque-
Cirque and alpine glaciers originate high in the mountains and flow downslope. They are called "cirque glaciers" if they originate in small bowls with steep headwalls
Hanging-
A hanging glacier originates high on the wall of a glacial valley and descends only part of the way to the surface of the main glacier and abruptly stops, typically at a cliff.[1] Avalanching and icefalls are the mechanisms for ice and snow transfer to the valley floor below.[1]
Piedmont-
If a valley glacier spills out of the mountains, onto the flat foreland, the ice often spreads to form a lobe. Then it is called a piedmont glacier.
Ice sheet/continental-
Ice Stream-
Ice streams are corridors of fast ice flow (ca. 0.8 km/year) within an ice sheet and are responsible for discharging the majority of the ice and sediment within them. Consequently, like the arteries in our body, their behaviour and stability is essential to the well being of an ice sheet.
Calving-
Calving is when chunks of ice break off at the terminus, or end, of a glacier. Ice breaks because the forward motion of a glacier makes the terminus unstable. We call these resulting chunks of ice “icebergs.” Icebergs can be BIG.
Marine Ice Shelf Instability-
The Marine Ice Sheet Instability hypothesis is that atmospheric and oceanic warming could result in increased melting and recession at the grounding line on a reverse slope gradient[12]. This would result in the glacier becoming grounded in deeper water and a greater ice thickness.
Ice Shelf Buttressing-
Ice shelves slow the flow of the ice sheet by pushing back against the glaciers that feed them, helping to slow their flow by acting as a buttress, or a braking system for the ice. As ice shelves flow out over bays and inlets they may run into obstacles, such as peninsulas, islands or ice rises.
Landscape features by:
Erosion:
Hanging valley-
Glaciers form U-shaped valleys through erosion. Hanging Valleys are found high up on the sides of larger U-shaped valleys. Hanging valleys begin as corries, but over time, more and more erosion creates an elongated corrie or a small U-shaped valley.
Aretes-
An arête is a thin, jagged crest that separates—or that once separated—two adjacent glaciers. These rugged ridgelines often look like serrated knives or saw blades, with steep sides and a sharp crest. The low points on the serrated surface are known as cols.
Horns-
Horns are pointed peaks that are bounded on at least three sides by glaciers. They typically have flat faces that give them a somewhat pyramidal shape and sharp, distinct edges.
Striation-
Glacial striations are a series of long, straight, parallel lines or grooves scratched onto a bedrock surface by rock fragments lodged in the base of a moving glacier. They typically form on hard rock, such as quartzite, that is relatively resistant to erosion.
Roche Mountonnee-
Roches moutonnées are asymmetric bedrock bumps or hills with a gently sloping and abraded up glacier (stoss) face and a quarried (or plucked) downglacier (lee) face that is typically blunter1,2. A good example of a roche moutonnée is shown in the image below.
Depositional-
A moraine is material left behind by a moving glacier. This material is usually soil and rock. Just as rivers carry along all sorts of debris and silt that eventually builds up to form deltas, glaciers transport all sorts of dirt and boulders that build up to form moraines.
Terminal Moraines-
A terminal, or end, moraine consists of a ridgelike accumulation of glacial debris pushed forward by the leading glacial snout and dumped at the outermost edge of any given ice advance. It curves convexly down the valley and may extend up the sides as lateral moraines.
Recessional Moraine-
A recessional moraine consists of a secondary terminal moraine deposited during a temporary glacial standstill. Such deposits reveal the history of glacial retreats along the valley; in some instances 10 or more recessional moraines are present in a given valley, and the ages of growing trees
Lateral Moraine-
Lateral moraines are sharp-crested piles of glacially-transported rocks and debris that are dropped by the ice as it melts. They form only in the ablation zone of a glacier (where more ice is melting than is accumulating as snow each year).
Medial Moraine-
Medial moraines form where two tributary glaciers come together. They are generally surficial features on the ice and often consist of rock that has fallen from a rockwall where the glaciers converge. Because they are thin, surficial features, medial moraines are rarely preserved after the ice retreats.
Kettle-
Kettles form when a block of stagnant ice (a serac) detaches from the glacier. Eventually, it becomes wholly or partially buried in sediment and slowly melts, leaving behind a pit. In many cases, water begins fills the depression and forms a pond or lake—a kettle.
Moraine-dammed lake-
A moraine-dammed lake, occurs when the terminal moraine has prevented some meltwater from leaving the valley. When a glacier retreats, there is a space left over between the retreating glacier and the piece that stayed intact which holds leftover debris (moraine). Meltwater from both glaciers seep into this space creating a ribbon-shaped lake due to the pattern of ice melt. This ice melt may cause a glacier lake outburst flood, leading to severe damage to the environment and communities nearby. Examples of moraine-dammed lakes include:
Proglacial Lakes-
In geology, a proglacial lake is a lake formed either by the damming action of a moraine during the retreat of a melting glacier, a glacial ice dam, or by meltwater trapped against an ice sheet due to isostatic depression of the crust around the ice.
Periglacial Processes-
● shattering (wedging, splitting) mechanical weathering (disintegration) caused by force of ice and dense water in fractures. ● heave. displacement of soil and rock with the growth of segregated ground ice as free water migrates to the freezing plane (lower vapour pressure) ... ● cracking.
Permafrost-
Permafrost is any ground that remains completely frozen—32°F (0°C) or colder—for at least two years straight. These permanently frozen grounds are most common in regions with high mountains and in Earth's higher latitudes—near the North and South Poles.
Pingo-
Pingos are ice-cored hills that form in recently drained lakes. The unfrozen ground under the lake is surrounded by permanently frozen ground called permafrost. After the lake drains, water in the saturated lakebed expands as it freezes, pushing excess water inwards toward the centre of the lakebed.
Sea Ice-
Ice Floe-
a sheet of floating ice.
Draft vs. Freeboard-
Measurements of ice depth below the waterline (or draft) by submarine sonar or radar systems can give good estimates of ice thickness provided there isn't too much snow (which is less dense than ice) on top. Sea ice freeboard is the difference between the height of the surface of sea ice and the water in open leads.
Pressure Ridge-
A pressure ridge, when consisting of ice in an oceanic or coastal environment, is a linear pile-up of sea ice fragments formed in pack ice by accumulation in the convergence between floes. Hypothetical interaction between two floes, resulting in a pressure ridge —— a linear pile-up of sea ice fragments.
Frazil Ice-
Frazil ice is a kind of slush ice. It can form in watercourses when cold air temperatures and wind chill combine to cause surface water temperature to be super-cooled (i.e. cooled below the freezing point). The super-cooled water is unable to form a solid ice cover because the water is moving or flowing fast.
Pancake Ice-
thin new ice such as forms in the early fall in polar regions in pieces about one to six feet in diameter resembling pancakes.
Glacial Hydrology-
Surface melt-
Surface melting refers to the process where the upper layer of ice or snow melts due to increased temperatures and solar radiation. This phenomenon is crucial in understanding cryosphere changes, as it affects ice sheets, glaciers, and sea ice, contributing to overall sea-level rise and alterations in local ecosystems.
Moulin-
A moulin is a roughly circular, vertical well-like shaft formed where a surface meltstream exploits a weakness in the ice. The term is derived from the French word for mill. They can be up to 10 meters wide and are typically found on ice sheets and flat areas of a glacier in a region of transverse crevasses.
Glacial isostatic adjustment (GIA): This term describes the overall process of the Earth's crust responding to the loading and unloading of ice sheets, including both the sinking during glaciation and rebounding after deglaciation. ● Forebulges: When a large ice sheet forms, the surrounding land can be pushed upwards, creating raised ridges called "forebulges" at the edges of the ice sheet due to the displaced mantle material. ● Post-glacial rebound: This is the specific term for the ongoing uplift of land following the retreat of a glacier, causing the previously depressed land to gradually rise back to its original elevation. ● Impact on sea level: As land rebounds in formerly glaciated areas, it can contribute to local changes in sea level, potentially affecting coastal regions. ● Example of isostatic effects: Scandinavia: This region is experiencing significant post-glacial rebound due to the melting of large ice sheets during the last glacial period, causing the land to rise even today.
History of Ice on earth-
Drop Stones-
Dropstones are clasts which pose a hydrodynamic paradox or which have an exotic or extra-basinal lithology with uncertain provenance. Recently, dropstones have been consistently interpreted as the product of ice rafting, and have been used to substantiate the presence of cool climatic phases in the geological record.
Striations-
Glacier scientists often use striations to determine the direction that the glacier was flowing, and in places where the glacier flowed in different directions over time, they can tease out this complex flow history by looking at the layered striations. These striations indicate that the direction of glacial movement in Africa was toward the Atlantic ocean basin and in South America was from the Atlantic ocean basin. This evidence suggests that South America and Africa were once connected, and that glaciers moved across Africa and South America.
Sedimentary deposits-
Sedimentary deposits, particularly glacial till and moraines, left behind by glaciers act as a key indicator of past glacier movement and history, allowing geologists to reconstruct the extent, direction, and timing of glacial advances and retreats by analyzing the composition, texture, and location of these deposits across a landscape; essentially acting like "footprints" of the glacier's past activity.
Interpreting glacial deposits: ● Composition: The type of rocks found within glacial till can indicate the source area of the glacier. ● ● Grain size: Variation in particle size within a deposit can reveal information about the glacial environment (e.g., meltwater activity). ● ● Clast fabric analysis: Studying the orientation of larger clasts within the till can help determine the direction of ice flow.
● Dating glacial deposits: ● Relative dating: Comparing the position of different glacial deposits to understand the sequence of glacial events. ● ● Radiometric dating: Techniques like optically stimulated luminescence (OSL) can be used to date specific sediment grains within the deposits.
Neoproterozoic Era-
A "Neoproterozoic Snowball Earth" refers to a period in Earth's history during the Neoproterozoic Era (around 720-635 million years ago) when scientists believe the entire planet may have been covered in ice, essentially resembling a giant snowball, due to extreme global glaciation, with ice sheets potentially reaching near the equator; this is considered to have been a series of severe ice ages where the planet experienced near-total ice cover, with the most prominent glacial periods occurring during the Cryogenian period within the Neoproterozoic era.
Late Paleozoic ice ages-
The late Palaeozoic ice age (LPIA) started around 340–330 million years ago (Ma)1. It is one of the most prominent glacial events in Earth's history, now seen as a dynamic succession of ice advances and retreats over Gondwana
Eocene oligocene transition and the impact of opening oceanic seaways
such as the drake passage-
The opening of the Drake Passage, a seaway between South America and
Antarctica, is widely considered a key factor in the Eocene-Oligocene transition (EOT), a major climate shift marked by global cooling and the initiation of significant Antarctic glaciation, as it allowed for the development of the Antarctic Circumpolar Current (ACC) which effectively isolated Antarctica and facilitated ice sheet growth; essentially, the opening of this passage played a significant role in the transition from a relatively warm, ice-free world to a cooler, more glaciated one by disrupting ocean circulation patterns and enabling the thermal isolation of Antarctica.
Larsen B.-
Larsen B. The collapse of Larsen B, showing the diminishing extent of the shelf from 1998 to 2002. From 31 January 2002 to March 2002 the Larsen B sector partially collapsed and parts broke up, 3,250 km2 (1,250 sq mi) of ice 220 m (720 ft) thick, an area comparable to the US state of Rhode Island.
Laurentide Ice Sheet-
After 20,000 years ago, Earth started to warm, and the Laurentide Ice Sheet began to disappear. By 8,000 years ago, the Laurentide Ice Sheet was a fraction of its original size, confined mostly to modern day Quebec and Labrador, a size and latitude broadly similar to that of the modern Greenland Ice Sheet. Paleolithic age.
Thwaites Glacier-
Between 1992 and 2017, Thwaites Glacier retreated at between 0.3 km (0.19 mi) and 0.8 km (0.50 mi) annually, depending on the sector, and experienced a net loss of over 600 billion tons of ice as the result. This loss had caused about 4% of the global sea level rise over that period.
structure and dynamics of glaciers and ice sheets. It can enable the detection of hidden processes such as brittle fracture, basal sliding, transient hydrological processes, and calving.
Gravimetry-
Gravimetry is used to study glaciers by measuring changes in Earth's gravitational field caused by mass variations in glaciers, essentially allowing scientists to monitor the gain or loss of ice mass on a large scale by detecting how the gravity pull varies over a glacier's surface, most commonly done through satellite data from missions like GRACE (Gravity Recovery and Climate Experiment) which track subtle shifts in the Earth's gravity field caused by changes in ice mass; this data helps to assess glacier melting and ice sheet dynamics over time.
Ice cores-
Ice cores act as valuable archives of past environmental conditions by trapping air bubbles containing ancient atmospheric gases like carbon dioxide and methane, preserving particles like dust and volcanic ash (aerosols), and recording variations in stable isotope ratios within the ice itself, which can be used to reconstruct past temperatures and precipitation patterns; essentially providing a detailed snapshot of climate history over long time periods.
Key aspects of ice core analysis:
Gases trapped in air bubbles: The most significant information from ice cores comes from the air bubbles trapped within the ice, which directly reflect the atmospheric composition at the time of snow deposition, allowing scientists to measure past concentrations of greenhouse gases like CO2 and methane, crucial for understanding climate change. Aerosols: Dust, volcanic ash, and other particles deposited on the snow surface become incorporated into the ice, providing information about past volcanic eruptions, dust storms, and even changes in wind patterns. Stable isotope analysis: By analyzing the ratio of oxygen isotopes (particularly δ18O) within the ice, scientists can infer past temperatures, as heavier oxygen isotopes tend to be more prevalent in colder conditions.
How ice cores are used to study past environments:
Reconstructing climate cycles: By analyzing the variations in gas concentrations and stable isotope ratios within an ice core, scientists can reconstruct past climate cycles, including glacial and interglacial periods, and identify periods of rapid climate change. Volcanic eruption records: The presence of distinct ash layers in ice cores provides a detailed record of past volcanic eruptions, including their timing and intensity. Pollution studies: Ice cores can also reveal information about past human activities by detecting elevated levels of pollutants like lead or sulfate aerosols.
Important points to consider:
Location matters: Ice cores from different regions, like Greenland and Antarctica, provide different perspectives on past climate conditions depending on their geographic location and local atmospheric conditions. Dating ice cores: Accurate dating of ice core layers is critical for interpreting the climate records, often achieved using techniques like counting annual layers and radiometric dating.
Overall, ice cores serve as a valuable tool for paleoclimatology, providing a unique record of past environmental conditions and allowing scientists to study how the Earth's climate has changed over long time scales.
Hazards-
Generally, rock avalanches are the result of bedrock slope failures. Here, large amounts of material break off intact rock and travel at high speeds downslope, breaking apart even further as they travel 6. As a result, huge deposits of material on the glacier surface (as can be seen in Figure 2).
Rock avalanches are not to be confused with rockfalls. A rockfall is simple the movement of already loose material thus are generally much smaller than rock avalanches 2.
Generally avalanching is the most widely studied mass movement event 1 and has huge impacts in populated valleys across Scandinavia and Central Europe.
Snow and ice avalanches can begin in three ways (Figure 3), causing large volumes of material to be released downslope.
Not only can avalanches have direct impacts in the valleys below, they can also lead to secondary impacts if avalanches dam rivers or enter glacial lakes causing outburst 1Landslides and debris flows (made up of a water-debris mix, usually 50-70% sediment) generally originate from steep slopes, talus slopes, and fluvioglacial deposits 5.
As a result, they are most common in periglacial and paraglacial environments due to the abundance of loose materials 9,10.
Often triggered by precipitation 11 these types of mass movement can significantly transform the landscape, altering channel morphology, rerouting rivers, and forming lakes 3.
