Internal/External Forces of the Earth

Inner Structure of the Earth 1.Inner Core—dense and solid 2.Outer Core—Molten or liquid Both are mostly hot and made of hot metal (iron)

Inner Structure of the Earth 3. Mantle—thick layer of rock (1800 miles thick); mostly solid, but has pockets of magma (melted rock)

4. Crust—very thin layer; rocky surface · Below the oceans, the crust is about 5 miles thick. Below the continents it averages miles in thickness.

Inner Structure of the Earth

Internal Forces that Shape Landforms 1.Volcanoes—form when magma inside the earth breaks through the crust. Lava flows and may produce a large, cone-shaped mountain

Internal Forces that Shape Landforms 2. Fault—a break in the earth’s crust. Movement along a fault can send out shock waves, causing an earthquake.

1.The lithosphere—the earth’s crust and upper layer of the mantle—are broken into a number of large, moving plates. The Plate Tectonic Theory

2. The plates slide very slowly over a hot, pliable layer of mantle. 3. The earth’s oceans and continents ride atop of the plates. The Plate Tectonic Theory

Primary Landforms Landforms created by tectonic activity are called primary landforms.

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.

The Ring of Fire

2. Hot Spots: hot regions deep within the mantle that produce magma, which rises to the surface. Volcanic island chains form as oceanic plates drift over the hot spot. Example: Hawaiian Islands.

What Happens When Plates Meet?

They collide and push slowly against each other and form a collision or converging zone. If 2 oceanic plates collide, 1 slides under the other. Islands often form this way. Converging (Collision) Zone

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

Himalayas

Oceanic lithosphere subducts underneath the continental lithosphere Oceanic lithosphere heats and dehydrates as it subsides The melt rises forming volcanism E.g. The Andes Subduction

They meet, or CONVERGE and form a subduction zone. *If an oceanic plate collides with a continental plate, the heavier oceanic plate will slide under the lighter, continental plate. Results: volcanic mountain building and earthquakes.

Spreading Zone

Plates pull away from each other and form a spreading zone. These areas are likely to have earthquakes, volcanoes, and rift valleys (a large split along the crest of a mountain). SPREADING ZONE

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

Iceland has a divergent plate boundary running through its middle Iceland: An example of continental rifting

At a FAULT, the plates will grind or slide past each other rather than colliding. Example: San Andres Fault. Fault

External Forces of the Earth

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.

Weathering Changes in the earth’s surface over thousands or millions of years Breaks down rock at or near the earth’s surface into smaller pieces

Frost Wedging: ice breaks down rocks

Chemical Weathering Alters the rock’s chemical make-up by changing the minerals that form the rock. Most important forces are water (H 2 O) and carbon dioxide (CO 2 ).

Chemical Weathering Carbonic Acid: CO 2 from the air or soil combines with H 2 O to make carbonic acid. When the acidic water seeps into the cracks in certain rocks (limestone) it dissolves the rocks away. Examples: caves

Chemical weathering Acid Rain: Chemicals in the polluted water combine with water vapor and then fall back to the earth as acid rain. Acid rain destroys wildlife, pollutes water, destroys forests, and eats the surface of buildings, statues, and natural rock formations.

Chemical Weathering Acid Rain is known to be caused by industrial pollution, volcanic activity, and acid producing agents in the oceans.