10_Earth Processes and Groundwater

WEATHERING, EROSION, GROUNDWATER, SINKHOLES

Course Information

  • Course Code: ESC1000C

  • Instructor: Dr. Jackie Miranda

  • Date: February 19, 2024

AGENDA

  • 60 Second News Update

  • Weathering

  • Soil and Erosion

  • Groundwater

  • Groundwater and Karst Topography

  • Lab 2025

  • Earth Processes and Groundwater

EARTH’S PROCESSES

Definitions

  • Weathering: Disintegration and decomposition of material at or near the surface.

  • Erosion: Incorporation and transportation of material by water, wind, or ice.

  • Mass Wasting: Transfer of rock material downslope due to gravity.

WEATHERING

Overview

  • Involves breaking down or dissolving of rocks and minerals.

  • Agents of weathering include:

    • Water

    • Ice

    • Acids

    • Salts

    • Plants

    • Animals

    • Temperature changes

Types of Weathering

Mechanical Weathering

  • Definition: Physical breakdown of rocks into smaller pieces.

  • Processes:

    • Pressure: Quick changes when rocks are lifted to the surface.

    • Frost Wedging: Ice expansion that breaks apart rocks.

    • Root Wedging: Plant roots expanding in cracks.

    • Salt Expansion: Evaporation in marine environments causes growth in salt crystals.

Chemical Weathering

  • Definition: Alters internal mineral structures by losing or gaining elements.

  • Processes:

    • Carbonic Acid Formation: Breaks down silicate rocks.

    • Dissolution: Minerals dissolve in water; can lead to karst topography.

    • Oxidation: Bonding of oxygen with minerals; creates rust.

Human Impact on Weathering

  • Although a natural process, human activity accelerates weathering:

    • Pollution: Increases weathering rates through acid rain formed by nitrogen oxides and sulfur dioxides.

Weathering and Climate

  • Mechanical Weathering: More common in cold, dry climates.

  • Chemical Weathering: Prevalent in warm, wet climates.

SOIL

Composition

  • Soil consists of minerals, organic materials, air, and water.

Soil Classes

  • Texture Classifications: Clay, silt, and sand; percentages determine soil texture.

Controls of Soil Formation

  • Factors influencing soil:

    • Parent material

    • Time

    • Climate

    • Vegetation

    • Topography (angle and orientation of slope influences soil development)

Soil Horizons

  • O (Organic Material): High in organic content.

  • A (Topsoil): Contains minerals and organic matter.

  • E (Eluviated): Leached of minerals and organic matter.

  • B (Subsoil): Enriched with minerals.

  • C (Parent Material): Minimals affected.

  • R (Bedrock): Solid rock beneath the soil.

EROSION

Definition

  • Geological process where earthen materials are worn away and transported by forces like glaciers, wind, and water.

  • Opposite of deposition.

Causes of Erosion

  • Major Agent: Liquid water (followed by wind and ice).

  • Mechanism: Raindrops dislodge soil, flowing water carries it away.

Factors Impacting Erosion

  • Soil types

  • Climate

  • Topography

  • Vegetation

  • Tectonic activity

Human Influences on Erosion

  • Activities such as agriculture, deforestation, damming, overgrazing, and construction lead to increased erosion.

GROUNDWATER

Overview

  • Groundwater is the largest reservoir of liquid freshwater on Earth, found in aquifers – porous rock and sediment.

Water Distribution

  • Freshwater: 2.5% of Earth's water; 30% is groundwater.

Aquifers

  • Definition: Underground rock layers that contain groundwater; filled slowly and can deplete if overdrawn.

Groundwater Flow and Zones

  • Vadose Zone: Unsaturated layer from surface to water table.

  • Saturated Zone: All pores filled with water.

  • Water Table: Follows surface topography; fluctuates due to environmental conditions.

Types of Aquifers

  • Unconfined: Connected to surface.

  • Confined: Has low permeability layer restricting water flow.

KARST TOPOGRAPHY

Overview

  • Karst landscapes formed predominantly through the dissolution of limestone.

  • Features include sinkholes, caves, and absence of well-defined drainage.

Formation Processes of Sinkholes

  • Dissolution Sinkholes: Gradual depression formation as water erodes carbonate rocks.

  • Cover Subsidence Sinkholes: Sediment collapse into subterranean cavities.

  • Cover-Collapse Sinkholes: Sudden surface breaches due to continuous roof collapse.

Impact of Human Activities

  • Human activities, such as excessive groundwater extraction and pollution, can exacerbate the formation of sinkholes.