WED & Watersheds

Weathering

  • Definition: Breakdown of rocks into smaller pieces by physical or chemical means.

Types of Weathering

  • Mechanical Weathering:

    • Rocks are broken down by physical means without changing their chemical composition.
    • Agents of mechanical weathering include:
    • Wind
    • Ice
    • Water
    • Gravity

  • Chemical Weathering:

    • Breakdown of rocks and minerals by chemical means.
    • Key processes include:
    • Oxidation: Reaction with oxygen that alters the mineral structure.
    • Dissolving: Substances dissolving in water can lead to rock breakdown.

  • Biological Weathering:

    • Caused by living organisms.
    • Examples:
    • Plant roots growing into cracks in rocks, breaking them apart.
    • Animals burrowing and exposing rock at the surface.
    • Microorganisms excreting acids that chemically alter the rock.

Factors Affecting Weathering

  • Composition:

    • Different minerals weather at different rates.
    • Example: Quartz is resistant, while calcite weathers easily.

  • Climate:

    • Cold climates favor mechanical weathering.
    • Wet climates enhance chemical weathering.

  • Surface Exposure:

    • Greater surface area leads to faster weathering processes.

Erosion

  • Definition: Movement of sediment by various forces such as water, wind, ice, and gravity.

Landforms Resulting from Weathering and Erosion

  • Canyons
  • Ridges and Valleys
  • Coastal Features:
    • Headland, Blowhole, Stack, Arch:
    • Formed through processes of erosion and undercutting along coastlines.

Karst Topography

  • Definition: Landscape shaped by dissolution of soluble rocks (like limestone).
  • Common features include sinkholes and caves.
  • Example: Virginia Cave and Karst Trail.

Deposition

  • Definition: The laying down of sediments after they have been transported.
  • Examples:
    • Moraine: Accumulation of soil and rocks formed by glaciers.
    • Beaches
    • Delta

Soil Formation

  • Process: Weathering, erosion, and deposition contribute to soil formation.
  • Soil Composition: A mix of rock fragments, organic material, water, and air, capable of supporting vegetation.

Importance of Soil

  1. Provides nutrients for plants.
  2. Offers habitats for various plants and animals.
  3. Stores and allows infiltration of water, supporting plant life.

Watersheds

  • Definition: An area of land where all water drains into a common body, such as a creek or river.
  • Key Components:
    • Tributary: A stream flowing into a larger body of water.
    • Watershed Divide: A boundary separating different watersheds.

Functions and Importance of Watersheds

  • Supply drinking water.
  • Provide water for agriculture and manufacturing.
  • Offer recreational opportunities and habitats for various life forms.

Drainage Basins of Virginia

  • Major systems include the Chesapeake Bay, Potomac, and Rappahannock rivers.

Chesapeake Bay Watershed Overview

  • Covers 64,000 square miles.
  • Contains 11,684 miles of shoreline.
  • Home to over 18 million people and significant biodiversity.

Summary

  • Weathering, erosion, and deposition are interconnected geological processes shaping landscapes.
  • Understanding these processes is crucial for environmental conservation and management.