How Landforms Are Created

Primary Landforms

Plate Tectonics – The earth’s surface is

broken up into large plates that are constantly moving and bumping into one another. Landforms created by tectonic activity are called primary landforms.

Tectonic plates are huge slabs of rock that float on liquid rock just below the earth’s crust. They move but often in different directions. Continents and oceans sit on these huge plates.

About 225 million years ago, all of the Earth’s landmasses were joined into one landmass called Pangaea. As time went on, the continents separated and moved to their current locations.

Divergent plate boundaries are areas where two plates move away from each other. As they move apart, new crust is formed by magma that is pushed up.

Mid-Atlantic Ridge

Convergent and Transform plate boundaries occur when tectonic plates push against each other.

Convergent plate boundaries can occur when two continental plates push against each other. This collision produces high mountain ranges.

Convergent plate boundaries also occur when a continental plate and an ocean plate move against each other. Because the continental plate is thicker, it slides over the thinner ocean plate. The downward force of the lower plate causes molten rock to build up. Then, as magma, it erupts to form volcanic mountains.

Sometimes two plates do not meet head-on but move alongside each other. This creates a Transform plate boundary or fault. Violent earthquakes can occur near these faults.

Secondary Landforms Landforms that are formed from the broken

down remains of primary landforms are called secondary landforms. Primary landforms become secondary landforms through the process of erosion.

Erosion

• Water is the most common force that erodes and shapes land

• Glaciers are large rivers of ice that have the force to move tons of rock.

• Wind can lift soil and carry it great distances and deposit it in dunes, and winds that carry sand can wear down rock.

Examples of Primary and Secondary Landforms

Mountains are primary landforms because they are created by tectonic activity. Over time, these mountains can be worn down by erosion to become hills. These hills would be secondary landforms.

Erosion

Primary Landform Secondary Landform