Glacial Modification
Glacial Modification of Terrain
Page 1: Introduction to Glacial Modification
Overview of the impact of glaciers on landscape features.
Page 2: Agenda
Types of Glaciers
Past/Present Glaciations
Formation and Movement
Effects of Glaciers
Page 3: The Pleistocene Epoch
Definition: The Pleistocene was an epoch that occurred approximately 2.6 million years ago, characterized by repeated glacial and interglacial climatic cycles.
Historical Glacial Cycles: Changes occurred over the past 450,000 years, visualized on a temperature graph showing glacial and interglacial periods.
Page 4: Impact of the Pleistocene
Significantly altered the topography created in previous epochs.
Evidence of glacial action is still visible in many continental terrains today.
Importance as agents of terrain shaping is evolving, especially in light of contemporary climate change.
Page 5: Equilibrium Line Altitude (ELA)
Defined as the altitude where accumulation equals ablation (melting) of glaciers over a year.
Sensitive to climatic variations: winter precipitation, summer temperatures, and wind-driven snow.
Glacial Processes: Snow accumulation leads to the formation of glacial ice in a series of transitions.
Page 6: Types of Glaciers
Formation: Result from the accumulation and compaction of snow.
Movement: Ice motion under gravity reshapes and deposits rocks, altering landscapes. Glaciation increases erosion by ten times compared to non-glaciated regions.
Page 7: Glacier Movement Patterns
Types of glaciers are characterized by movement patterns:
Mountain Glaciers: Found in high-altitude areas, such as polar regions.
Continental Ice Sheets: Cover broader areas of land.
Glacial processes yield both constructive and destructive landforms.
Page 8: Continental Ice Sheets
Definition: Form in non-mountainous, high-latitude polar environments.
Area: Ice sheets extensively cover Greenland (80%) and Antarctica (90%).
Page 9: Key Ice Sheets
Greenland Ice Sheet
Antarctic Ice Sheet
Page 10: Ice Dynamics
Outlet Glaciers: Valley glaciers that drain inland ice sheets and flow through mountain gaps.
Ice Shelves: Portions of ice sheets that spread over ocean.
Page 12: Ice Calving
Definition: Process where chunks of ice break off from glaciers and ice shelves and fall into the sea.
Page 13: Mountain Glaciers
Characteristics: Confined by surrounding terrain, often referred to as alpine glaciers.
Function: Flow down valleys, increasing in size as they absorb smaller glaciers.
Page 14: Global Presence of Mountain Glaciers
Found in regions like the Rockies, Andes, Himalayas, and Arctic mountains.
Page 15: Types of Mountain Glaciers
Piedmont Glaciers: Form when valley glaciers extend beyond their valleys onto flat plains.
Page 20: Past and Present Glaciations
Variability in Glacial Ice Volume: Historical changes significant for understanding past climates.
Page 21: Pleistocene Glaciation
Timeline: Began approximately 2.59 million years ago, with significant ice retreats last occurring about 9,000 years ago.
Characteristics: Major cooling of high-latitude, high-elevation areas.
Page 22: Current Epoch: Holocene
Follows the Pleistocene, marking a period of interglacial conditions.
Page 23: Maximum Ice Coverage
At the peak of Pleistocene, one-third of the land was covered in ice; joined by distinctive areas like the Driftless Area in Wisconsin.
Page 25: Periglacial Processes
Areas affected by glacial effects without direct ice presence; characterized by events like erosion due to ice melt.
Page 26: Sea-Level Changes
Accumulation of ice on land leads to global sea-level drops, exposing land bridges and altering coastlines.
Page 30: Crustal Depression
Ice weight causes continents to sink; subsequent melting results in rebound effects.
Page 36: North American Glaciers
Focused in mountainous regions, particularly in the Pacific Northwest and Alaska.
Page 37: Climate Change Indicators
Observations show retreat of polar ice caps and increased melting rates as indicators of warming.
Page 39: Glacier Formation and Movement
Formation begins with snow transitioning to ice via compression; movement impacted by balance between accumulation and ablation.
Page 47: Glacial Flow and Advance
Flow vs. Advance: Glaciers always flow but not necessarily advance; dynamic changes with climatic conditions.
Page 49: Erosive Power of Glaciers
Glacier erosion is powerful, consisting primarily of glacial plucking and abrasion.
Page 50: Glacial Plucking
Defined by the picking up of rock materials through refreezing of meltwater and hydraulic action.
Page 51: Glacial Abrasion
Narrated by the rough texture it imparts on bedrock as debris in glacial ice grinds surface. Produces striations indicative of past glacial flow.
Page 55: Transportation by Glaciers
Glaciers carry large rock pieces, primarily through the motion of glacial flour, fine sediment produced by glacial erosion.
Page 60: Deposition by Glaciers
Deposition occurs as glaciers transport and redistribute materials in new forms, including drift and glacial erratics.
Page 71: Kettles Formation
Kettles are depressions formed by melting blocks of ice, often leading to lakes and ponds.
Page 75: Glaciofluvial Features
Deposition shapes created by ice-sheet meltwater, forming features such as outwash plains.
Page 76: Outwash Plains and Features
Typically flat areas formed in front of melting glaciers, characterized by sediment sorting due to water movement.
Page 84: Mountain Glacier Erosion
Cirques are key features where alpine glaciers originate, shaping mountain landscapes.
Page 85: Cirques Definition
Bowl-shaped depressions carved by glaciers often water-filled (tarns) post-retreat.
Page 94: Glacial Troughs
Transformation of V-shaped valleys to flat-bottomed U-shaped troughs as glaciers deepen, steepen, and widen valleys.