Earth's Land Relief and Geological Processes

Land Relief and the Geological Process

Land relief is the roughness and deformation of the Earth's crust. There are five factors that influence it:

• Lithological: These involve soft rocks and hard rocks.
• Structural: The shape and arrangement influence land relief.
• Dynamic: The processes involved in building the landscape.
• Climatic: The impact of different climates.
• Anthropic: These factors are related to human activity.

External processes are driven by the sun, while internal processes originate from the Earth's internal energy.

The Modelling of the Landscape

Features such as mountains and valleys define the terrain. Internal processes create the large architectural features of the landscape.

Agents and Sources of Energy

An external agent is a material body which produces changes in geological materials, such as water, air, and living beings. The main source of energy for these agents is solar radiation. Additionally, gravity makes objects move continuously from high to low positions.

Processes, Factors, and Forms

• Aeolian processes: These originate from the action of the air.
• Torrential fluvial: The action of fresh water.
• Marine: Produced by the action of the seas and oceans.
• Glacial: Derived from the action of masses of ice.
• Biotic: Caused by living beings.
• Anthropic: The result of human activity.

Meteorization and Rock Alteration

Meteorization (weathering) is an alteration of the rock. The difference between meteorization and erosion is that the fragments in meteorization remain in the same place, whereas in erosion, they are transported away.

Physical and Chemical Meteorization

Physical meteorization occurs when rock is fragmented, broken, or pulverized by the action of mechanical processes. Chemical meteorization of a rock takes place when the atmospheric agents of the hydrosphere act on the rock and transform its minerals.

The Composition and Formation of Soil

The soil is a natural aggregate of variable thickness that covers the surface of the Earth. Five factors influence its formation:

• Mother rock: The original geological matter from which soils are formed.
• Climate: Influences the speed and type of the soil formation process.
• Living beings: Help to mix the materials and help to air the soil.
• The position of the landscape: The topography influences the formation process.
• Passing of time: Gradually changes the soil characteristics.

The Action of Wild and Fluvial Waters

Wild waters occur when water flows without a fixed course. This creates badlands, which are abrupt areas with a V-shape, and fairy chimneys, which are conical shapes that appear when there is a spring.

Fluvial Erosion, Transport, and Sedimentation

The three fluvial stages are:

• Fluvial Erosion: This depends on friction. Gorges and ravines are formed where the river carves valleys. Waterfalls appear when water finds a drop, and meanders are curves in the course of the river.
• Fluvial Transport: The particles transported by the water move in different ways, such as being dissolved, jumping, or rolling.
• Fluvial Sedimentation: The sedimentation of different-sized particles occurs when the speed of the water decreases.

Common formations include alluvial plains (deposits of materials in valleys), fluvial terraces (layers of river deposits), and deltas (accumulations at the river mouth).

The Action of the Sea and Wind

Waves are movements of the surface water caused by the wind. Tides and currents involve the displacement of water in the sea. Marine erosion is a result of waves, creating forms such as cliffs (abrupt slopes) and abrasion platforms (flat surfaces slightly inclined toward the sea).

The Geological Action of the Wind

Aeolian erosion consists of two main processes:

• Deflation: The carrying of small particles by the wind.
• Corrasion: The wearing down of rocks caused by the impact of wind-blown particles.