Geological Processes Shaping Earth's Landscapes

Earth's Dynamic Surface: Landforms and Geological Processes

Factors Influencing Relief Formation

• Rock Type: Each rock possesses specific characteristics. For instance, granite can yield different forms of clay due to its composition.
• Climate: The predominant external geological agent in an area is determined by climate. In temperate regions, water is the most important agent, whereas in cold climates, ice is dominant.
• Structure of Materials: Rocks that have been folded or fractured provide initial conditions for their subsequent shaping and deformation.
• Relief Formation Processes: External geological agents remove materials from one place and deposit them in another, constantly reshaping the landscape.

Major Geological Agents and Their Effects

Water (Fluvial and Marine Processes)

• Surface Water: Active in most continental areas, particularly in temperate and tropical climates.
• Marine Water: Influences oceanic and coastal areas.
• Erosion by Water:
  • Depends on speed and flow.
  • Forms originated by differential erosion include waterfalls and fairy chimneys.
  • Gullies and ravines are common in alleyways or ravines.
  • V-shaped valleys are characteristic of mountain areas.
  • Trough valleys and floodplains are associated with flood periods.

Wind (Aeolian Processes)

• Wind Erosion:
  • Alveoli: Small hollows produced in rocks.
  • Mushroom Rocks: Wind abrasion forms isolated rock masses resembling mushrooms.
  • Desert Pavement: Most of the desert surface is covered by a thick carpet of rocks, formed by wind removing finer particles.
• Wind Deposition:
  • Dunes: Deposits of sand.
  • Loess: Deposits of fine materials.

Glaciers (Glacial Processes)

• Glacier Anatomy:
  • Cirque: The upper, bowl-shaped basin.
  • Tongue: The mass of ice that flows down the valley.
  • Terminal Area: Where the ice melts.
• Glacial Erosion:
  • U-shaped Valleys: Alpine glaciers excavate valleys with a characteristic U-shaped cross-section.
  • Hanging Valleys: Former glacial tributaries that enter the main valley at a higher elevation.
  • Glacial Lakes: Formed when the glacier over-excavates its cirque or basin, making the bottom deeper.

Gravitational Processes (Mass Movement)

• Detachment: Free fall of material.
• Glide/Slide: Sliding of block materials.
• Flow: Mass movement of low cohesive materials.
• Creep: Downslope displacement of loose materials, primarily affecting the surface layer.

Specific Landforms

Karst Landforms

Characterized by soluble rock dissolution, forming features such as sinkholes, pits, galleries, and caves. Inside caves, stalactites, stalagmites, and columns are common.

Granitic Landforms

Examples include berrocal (granite outcrops) and tors (isolated rock formations).

Earth's Internal Dynamics

Isostasy

The Earth's crust maintains a gravitational balance with the denser material in the interior. When the crust unloads (e.g., ice melts), it rises; when overloaded (e.g., sediment deposition), it sinks.

Plate Tectonics

The lithosphere is divided into a set of rigid pieces called lithospheric plates. Oceanic lithosphere is continually renewed, while continental lithosphere has a more permanent character. Lithospheric plates are mounted on the plastic sub-lithospheric mantle. Plate displacements are caused by energy from the Earth's interior, aided by gravitational energy.

Evidence for Plate Tectonics

• Geological: Discovery of geological formations with continuity across the Atlantic Ocean.
• Geographic: Consideration of continuous changes in sea levels and coastal erosion processes.

Types of Plate Boundaries

• Mid-Ocean Ridges: Divergent plate boundaries where new oceanic lithosphere is generated from material rising from the deep Earth's interior.
• Subduction Zones: Convergent plate boundaries where lithosphere is destroyed as one plate sinks beneath another.
• Transform Faults: Plate boundaries where plates move laterally past each other, with neither creation nor destruction of lithosphere.