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.