MEV 012: Unit 03 - Earth Surface Processes

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 UNIT 3: EARTH SURFACE PROCESSES

3.0 Introduction

The Earth's surface is continuously shaped and reshaped by various physical processes. These processes are responsible for forming diverse landforms like valleys, mountains, dunes, and coastal cliffs. Earth surface processes are primarily driven by natural agents such as water, wind, ice, and waves. Understanding these dynamic mechanisms is crucial for studying geomorphology, environmental science, and sustainable land use.

3.1 Objectives

By the end of this unit, learners will be able to:

  • Understand the different types of surface processes.
  • Identify various erosional and depositional agents.
  • Describe how rivers, glaciers, winds, and sea waves shape the Earth's surface.
  • Understand the processes of weathering, transportation, deposition, burial, and diagenesis.

3.2 Surface Processes

Earth surface processes refer to external forces that modify landforms through erosion, weathering, transportation, and deposition. These processes work at various scales—from gradual changes to sudden, dramatic events.

3.2.1 Erosional Agents

Erosion is the removal of soil, rock, or dissolved material from one location and its transport elsewhere by agents like:

  • Water (rivers, rainfall)
  • Wind
  • Ice (glaciers)
  • Waves

3.2.2 Weathering

Weathering is the breakdown of rocks at or near the Earth’s surface into smaller particles.

  • Mechanical Weathering: Physical breakdown (e.g., freeze-thaw, exfoliation)
  • Chemical Weathering: Alteration of rock composition (e.g., oxidation, carbonation)
  • Biological Weathering: Roots, lichens, and organisms breaking down rocks

3.2.3 Transportation

Once material is eroded, it is transported by:

  • Running Water: Carried as bed load, suspended load, or dissolved load
  • Glaciers: Push material as they advance or melt
  • Wind: Moves fine particles across deserts
  • Waves and Currents: Shift sediments along coastlines

3.2.4 Deposition

Deposition occurs when transporting agents lose energy and drop their load. It creates landforms like:

  • Deltas (rivers)
  • Moraines (glaciers)
  • Dunes (wind)
  • Beaches (waves)

3.2.5 Burial

Burial is the accumulation and compaction of sediments under layers over time. It initiates the transition from loose sediment to rock.

3.2.6 Diagenesis

Diagenesis includes all chemical, physical, and biological changes that sediments undergo after burial and before turning into sedimentary rock (lithification).

3.3 Depositional Features Formed by Rivers, Winds, Glaciers, and Coastal Processes

Different agents create distinct depositional landforms based on their energy and environmental context.

3.3.1 Stream Erosion, Transportation, and Deposition

  • Erosional Features: V-shaped valleys, waterfalls, gorges
  • Transportation: Sediments carried downstream in various loads
  • Depositional Features: Floodplains, levees, alluvial fans, deltas, meanders, oxbow lakes

3.3.2 Glacial Erosion, Transportation, and Deposition

  • Erosional Features: U-shaped valleys, fjords, cirques, arêtes
  • Transportation: Glaciers drag rocks and debris
  • Depositional Features: Moraines (lateral, medial, terminal), drumlins, eskers

3.3.3 Wind Erosion, Transportation, and Deposition

  • Erosional Features: Deflation hollows, mushroom rocks
  • Transportation: Fine particles like dust and sand carried by wind
  • Depositional Features: Sand dunes (barchan, transverse, star dunes), loess deposits

3.3.4 Sea Wave Erosion, Transportation, and Deposition

  • Erosional Features: Sea cliffs, caves, arches, stacks
  • Transportation: Longshore drift carries sediments
  • Depositional Features: Beaches, spits, bars, tombolos, lagoons

3.4 Let Us Sum Up

Earth surface processes are essential natural forces shaping the planet's landscape. From the slow action of weathering to the fast erosion by rivers and glaciers, each agent leaves a unique imprint. The balance between erosion and deposition results in diverse landforms that we see across deserts, coastlines, river plains, and mountainous regions.

A thorough understanding of these processes aids in disaster management, land-use planning, and environmental conservation.

3.5 Keywords

·         Erosion-The removal of surface material by natural agents like water, wind, or ice.

·         Weathering-The breaking down of rocks through mechanical, chemical, or biological means.

·         Transportation-The movement of weathered material from one place to another.

·         Deposition-Laying down of transported materials when energy decreases.

·         Burial-The accumulation and compaction of sediments under additional layers.

·         Diagenesis-Chemical and physical changes in sediments after burial, leading to lithification.

·         Delta-Depositional landform at river mouths formed by sediment accumulation.

·         Moraine-Glacially formed accumulation of unconsolidated debris.

·         Dune-Mound of sand formed by wind deposition.

·         Longshore Drift-Movement of sediment along the coast by wave action.

·         Fjord-Glacially carved, deep coastal inlet with steep sides.

·         Loess-Fine-grained silt and clay deposited by wind.

·         Alluvial Fan-Fan-shaped deposit formed by river sediment at the base of mountains.

·         Cirque-Amphitheater-like valley formed by glacial erosion.

·         Tombolo-A sand or shingle bar connecting an island to the mainland.

 

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