March

Glacial Depositional and Erosional Features

Glacial Depositional Evidence

  • Glacial Radix: An indicator of glacial movement, often associated with drop stones.
  • Glacial Till: Poorly sorted rock fragments of various sizes resulting from glacial activity.
  • Moraines: Landforms made of till, which include different types, such as:
    • End Moraine: The terminal moraine marks the furthest advance of a glacier.
    • Lateral Moraine: Forms on the sides of the glacier.
    • Medial Moraine: Created when two tributary glaciers combine, and their lateral moraines merge in between.
    • Ground Moraine: Spread out over a landscape as the glacier retreats.
  • Drop Stones: Rock fragments dropped by a melting iceberg, often surrounded by fine deposits from deep lake or marine environments.

Glacial Erosional Evidence

  • Glacial Striations: Grooves or scratches on the bedrock caused by the movement of glacial ice; indicates direction of glacial flow.
  • Glacial Polish: A smooth surface resulting from the abrasion of bedrock by a glacier.
  • U-Shaped Valleys: Formed by the deepening and widening effect of a glacier compared to a V-shaped valley formed by river erosion.
  • Hanging Valleys: Created by tributary glaciers that erode less deeply than the main glacier, leaving them at a higher elevation than the main valley.
  • Cirques: Bowl-shaped depressions carved by glaciers.
  • Aretes: Sharp ridges formed between two glaciers as they carve away at the surrounding rock.
  • Horn: A pointed peak formed by multiple glaciers eroding away the surrounding rock on several sides.

Alpine vs. Continental Glacier Features

  • Alpine Glacier Features: Includes cirques, hanging valleys, U-shaped valleys, fjords, horns, all associated with mountainous regions.
  • Continental Glacier Features: Involves moraines and includes different processes such as the formation of drumlins, kettles, and esker.

Deposition and Erosion Characteristics

  • Types of Moraines:
    • Lateral and Medial Moraines: Strictly associated with alpine glaciers due to the need for tributary glaciers.
    • End Moraines: Form when glacial movement is stationary, creating distinct landforms.
    • Ground Moraines: Occur during glacial retreat and can form distinct layers of sediment.

Drumlins and Their Origins

  • Drumlin: An elongated hill of glacial sediment that is asymmetrical, with a steep side indicating the direction from which the ice flowed. Typically formed from the smearing of sediment by glaciers.

Eskers, Kettles, and Patterns of Lakes

  • Esker: An elongated, sinuous hill formed by subglacial river flow beneath a glacier, made of sediments carried and deposited by the flow.
  • Kettle: A lake formed from stranded ice blocks that have melted, creating circular lakes in glacial outwash areas.
  • Tarn: A mountain lake found in a cirque; it captures glacier meltwater in depressions.
  • Paternoster Lakes: A series of lakes connected by streams in hanging valleys.

Glacial Zones and Processes

  • Zone of Ablation: Area where ice loss exceeds accumulation due to melting or calving of ice.
  • Zone of Accumulation: Area where snow accumulates and compacts into glacial ice.
  • Snow Line: The elevation above which snow persists year-round and can contribute to glacier formation.

Factors Affecting Glacier Formation

  • Glaciers can form at high altitudes, high latitudes, and locations near water, but primarily require land for significant formation.
  • Latitude vs. Altitude:
    • Latitude: The position north or south on the earth (affects temperature and snowfall).
    • Altitude: The height above sea level (affects temperature).

Tides and Their Influence on Coastal Areas

  • Tides: Variations in sea level caused by the gravitational pull of the moon and sun.
    • Tidal Range: The vertical difference between high and low tide, influenced by slope, latitude, and the moon's position.
    • Spring Tide: Occurs during a full or new moon, with higher high tides and lower low tides due to the alignment of the sun and moon.
    • Neap Tide: Occurs during the first and third quarters of the moon, resulting in lower high tides and higher low tides due to the sun and moon's positions being at right angles to each other.