Earth's Cryosphere: Glaciers and Ice Formation

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What distinguishes U-shaped valleys created by glaciers from V-shaped valleys formed by streams?

U-shaped valleys have a flat-bottomed profile, while V-shaped valleys are wider.

U-shaped valleys have a flat bottom with steep sides, while V-shaped valleys retain a narrow profile. (correct)

U-shaped valleys are formed by erosion at their bases only, while V-shaped valleys are formed at their sides.

U-shaped valleys are steeper-sided and narrower than V-shaped valleys.

Which feature forms at the head of a glacially carved valley due to the plucking of rock?

Cork

Cirque (correct)

Col

Arête

What is the primary material that makes up moraines left behind by glaciers?

Till (correct)

Diamictite

Sandstone

Striated rock

What type of moraine is formed at the end of a glacier?

Terminal moraine Signup and view all the answers

Which of the following correctly describes a drumlin?

An elongated, teardrop-shaped hill formed under a glacier. Signup and view all the answers

What primarily causes the formation of glaciers?

Accumulation of snow that does not completely melt in summer Signup and view all the answers

Which of the following correctly describes firn?

It is granular mass of ice crystals that forms as older snow is buried. Signup and view all the answers

Where are alpine glaciers primarily located?

In major mountain ranges and narrow valleys Signup and view all the answers

What is the primary difference between icebergs and glaciers?

Glaciers are stationary, while icebergs float and move. Signup and view all the answers

What retains records of the past atmosphere in solid glacial ice?

The presence of air pockets trapped within the ice. Signup and view all the answers

What characterizes the plastic zone of a glacier?

It contains a high pressure that allows ice to bend or flow. Signup and view all the answers

Which describes the zone of accumulation in a glacial budget?

It is the area gaining ice due to higher snowfall than melting. Signup and view all the answers

What is calving in relation to ice sheets?

The breaking off of ice edges to form icebergs. Signup and view all the answers

What primarily contributes to glacial retreat during warmer summers?

Rapid melting of ice exceeding accumulation. Signup and view all the answers

What did the study conducted on the Jungfraufirn Glacier in 1948 reveal about glacier movement?

The rigid surface ice is comparatively slower than the interior flow. Signup and view all the answers

Study Notes

Earth's Cryosphere: Glaciers and Glacial Landforms

The cryosphere (ice) has unique erosional and depositional features compared to the hydrosphere (liquid water).
Two primary forms of ice are glaciers and icebergs. Glaciers are year-round land-based ice accumulations. Icebergs are floating masses of ice, often originating from glaciers.
Glaciers cover approximately 10% of Earth's surface and are powerful agents of erosion.
They primarily form in mountainous areas with cold temperatures and high precipitation, as well as in extremely cold low-lying areas like Greenland and Antarctica.

Glacier Formation

Glaciers form from accumulated snowfall that doesn't melt completely in summer.
Perennial snow accumulates year-round, forming a snow field.
This snow compacts, bonds with underlying layers, and reduces void space between snow grains.
Buried snow layers compact into firn (névé), a granular ice crystal mass.
Further burial, compression, and recrystallization transform firn into glacier ice, retaining some air pockets.
These air pockets hold past atmospheric composition records.
Glacier types include alpine/valley, ice sheets, and ice caps.

Types of Glaciers

Alpine glaciers commonly occupy narrow valleys in major mountain ranges (e.g., Andes, Rockies, Alps, Himalayas).
They can also form at lower elevations in areas with high precipitation.
Ice sheets (continental glaciers) cover vast areas of land, like Greenland and Antarctica.
Greenland's Ice Sheet is the world's largest northern ice mass with over 2 million sq km area and up to ~1500 meters.
Antarctica's Ice Sheet is even larger, covering almost the entire continent, exceeding 4,000 meters thick in places.
Ice caps are smaller ice sheets (usually less than 50,000 km2) that occupy high elevations and mountaintops (Iceland).

Glacier Movement

Glacial ice flows downhill under its own weight.
Ice flow rates vary, fastest in the middle and slowest at the bottom.
Surface ice is rigid and brittle (up to ~50 meters), prone to crevasses (large cracks).
Pressure increases below the brittle zone (~100 kPa), promoting ductile ice flow (plastic zone).
Glacial sediments (boulders to silt/clay) act as grinding agents, significantly eroding bedrock.

Glacial Budget

A glacial budget assesses ice gain/loss (like a bank account).
Zone of accumulation (more snow than melt), where ice grows.
Zone of Ablation (more melt than snow), where ice shrinks.
Equilibrium line (snowline/firnline) marks the boundary between these zones. Its position changes seasonally and yearly based on glacial budget balance.
Warmer summers accelerate glacier retreat, cooling summers promote advance.
Current global warming rapidly contributes to sea-level rise.

Glacial Landforms

Glaciers create erosional and depositional landforms.
Erosional landforms are created by removal of material.
Depositional landforms are created by adding material.

Erosional Landforms

U-shaped valleys (v-shaped valleys are eroded by streams).
Arêtes (sharpened ridges).
Cirques (bowl-shaped depressions at glacier heads).
Tarns (lakes in cirques).
Horns (steep-sided, spire-shaped mountains).
Cols (mountain passes).
Hanging valleys (tributary valleys left high above the main valley).
Truncated spurs (steep, triangle-shaped cliffs).

Depositional Landforms

Drift (all glacial deposits).
Till (unsorted glacial sediment, containing various-sized clasts).
Tillite (lithified till).
Diamictite (lithified rock with varying clast sizes).
Moraines (mounded till deposits, classified by location relative to the glacier: terminal, recessional, lateral, medial, ground).
Outwash plains (silt, sand, and gravel deposited by meltwater streams).
Glacial erratics (large, mismatched boulders).
Kettles (depressions formed from melting ice blocks).
Kettle lakes (water-filled kettles).
Eskers (sinuous ridges of sediment deposited by meltwater channels in glaciers).
Kames (mounds of till deposited by meltwater).
Drumlins (elongated, asymmetrical hills shaped by ice flow).
Paternoster lakes (series of lakes formed by recessional moraines).
Finger lakes (long, glacially carved depressions).
Pluvial and proglacial lakes (lakes formed by precipitation during humid glacial periods or meltwater associated with glaciers, respectively). Examples include Lake Bonneville (Utah), Lake Missoula (Washington), and Lake Agassiz (Manitoba).
Channeled Scablands (landscape created by Missoula Floods).

Ice Ages and Sea Level Change

Glaciations occur when Earth's climate becomes cold enough for continental ice sheets to expand.
The recent Pliocene-Pleistocene glaciation involved several glacial cycles, reaching its maximum extent during the Last Glacial Maximum (26,500-19,000 years ago).
Milankovitch Cycles (variations in Earth's orbit and axial tilt) affect incoming solar radiation, triggering warming and cooling cycles within glaciations.
Sea level rises due to glacial meltwater and thermal expansion of seawater during warming trends.
Isostatic rebound (land rising after ice sheet melting) also affects relative sea level.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the unique features of Earth's cryosphere focusing on glaciers and glacial landforms. Learn about the processes of glacier formation and how these icy structures shape our planet's landscape. This quiz delves into the characteristics and significance of glaciers in erosion and deposition.