Classification and Features of Earth's Relief and Crusts

The Landscape and Earth's Relief

Relief is the aspect of the Earth's surface regardless of biotic elements.

Descriptive Classification of Landforms

• Mountain: Isolated relief with a large elevation difference between its base and top.
• Cerro (Hill): Isolated relief with a gentle gradient.
• Gorge or Throat: A narrow valley bottom featuring steep walls on its sides.
• Plateau: Isolated topography with a flat top.

Interpretative Classification of Relief Forms

• Mountains: Formed by the folding of material or volcanic activity. An alignment of ridges or mountains is called an orogen.
• Witness Hill (Cerro Testigo): Isolated relief whose summit is at the height that the surrounding area once reached in the past.
• Terraces: A fragmented and tiered zone, consisting of successive levels formed by river action.

Major Land Relief Forms

The Oceanic Crust

Composed of basalt, the oceanic crust forms the ocean basins and is covered almost entirely by water.

Specific Oceanic Relief Features

• Abyssal Plains: Very extensive submarine plains whose average depth is about 4,500 meters.
• Oceanic Ridges: Alignments of volcanoes characterized by intense lava flow.
• Isolated Volcanic Reliefs: Isolated volcanoes resulting from past volcanic activity.
• Ocean Trenches (Fosas Oceánicas): Elongated grooves where great depths are reached (e.g., the Mariana Trench). These are areas with intense seismic activity.
• Island Arcs: Volcanic ridges that emerge from the sea.

The Continental Crust

Basically formed by granite and metamorphic rocks, the continental crust is thicker and less dense than the oceanic crust, allowing it to rise above most oceans to form the continents.

Specific Continental Relief Features

• Peneplains: Vast plains resulting from erosion caused by geological agents. They typically have an average altitude between 300 and 600 meters.
• Mountain Ranges (Cordilleras): Alignments of mountains formed by the folding of material or volcanic activity.
• Rifts: Elongated depressions formed by the breaking, straining, and subsidence of the continental crust along large fractures.
• Continental Shelves: The part of the continental crust covered by the sea, typically up to 200 meters deep.
• Continental Slope: Represents the edges of continents, covering sloping areas situated between the continental shelf and the oceanic crust.