Forces That Shape the Earth

Earth’s Exterior-Spheres of the Earth

Earth’s Exterior & Interior-Layers of the Earth

Internal Forces That Shape the Earth-Plate Tectonics Earth’s crust is made of plates that float on magma. These plates were once together as the supercontinent “Pangaea” They have since spread apart

Plate Boundaries Earth’s plates fit together like a puzzle There are 3 types of plate boundaries Oceanic-oceanic Continental-continental Oceanic-continental

Plate Movement The plates that border each other move slightly as the float on the circulating magma This circulation results from convection Hot magma rises from the center of the earth towards the crust-as it moves away from the earth’s hot core, it cools down When it cools it becomes heavier and denser and sinks back downward

Plate Movement

Plate Tectonics: Plate Movement Four Types Divergent Convergent Subduction Collisional Faulting/Transform

Plate Movement: Divergent Boundaries

Plate Movement: Convergent Subduction

Plate Movement: Convergent Collisional

Plate Movement: Faulting/Transform Boundary

Plate Tectonics in Action

The Exception- Hot Spots plumes of stationary hot material plate moves slowly above it. spot melts through the plate like a blow torch creating a volcano above it. As the plate moves, the spot melts through another spot producing a chain of volcanic islands Hawaii is an example of a hot spot island chain.

External Forces That Shape the Earth-The Gradational Process Gradational forces tear down and build up the earth’s surface. They include: Weathering Erosion Deposition

Weathering is the process that changes the surface of exposed rocks Breaks rocks up into smaller bits 2 primary types of weathering Mechanical/Physical Breaking things by force Hitting, scratching, cracking (wedging) Chemical Chemical interactions

Mechanical Weathering Something gets in & actually breaks it wedging: something physically gets into the rock and expands breaking the rock Roots/Plant wedging Frost action Exfoliation: rubbing from something strips layers off the rock

Mechanical Weathering: Plant/Root Wedging Tiny root hairs seek out small cracks and pits in rock. Once the root hairs find a place they grow and expand. The expansion causes great pressure and cracks the rock.

Mechanical Weathering: Frost Action/Ice Wedging Water seeps into small cracks in rocks. When the water freezes it expands creating great pressure. The crack widens and allows water to seep deeper into the rock. The cycle continues over time

Mechanical Weathering: Exfoliation This occurs with abrasion from sediment moved by: Water Wind Rocks on rocks

Chemical Weathering rock material is changed into another substance by chemical reaction. Agents of chemical weathering Oxidation Hydration/Hydrolysis Acid precipitation

Chemical Weathering: Oxidation Chemical reaction between minerals and oxygen Combination creates rust

Chemical Weathering: Hydration/Hydrolysis Chemical reaction with water contact Hydration Water molecules are added to the composition of the material causing expansion and weakness that leads to breakage Hydrolysis Water dissolves and leaches out material that comes to the surface, turns to powder, and rubs off

Chemical Weathering: Dissolution Minerals are dissolved usually by water with high acidity CO2 emissions into the atmosphere create carbonic acid in precipitation and dew

What Factors Influence the Rate of Weathering? Amount of surface area exposed More surface= faster weathering Mineral composition Rock w/iron ore=oxidation Shale is flaky so breaks up more easily Climate Cold and/or dry climates favor physical weathering. Warm and wet climates favor chemical weathering. Frost action works best in areas where the temperature fluctuates wildly.

Erosion The second part of the gradational process Moves broken sediment through Water Wind Glaciers Gravity This process works in conjunction with deposition, the final phase of the gradational process In deposition eroded material is deposited creating new landforms

Erosion: Water

Erosion: Wind

Erosion: Glacial

Erosion: Gravity This is also known as mass movement or mass wasting Results when angle can no longer sustain weight a sudden release occurs Ex: avalanche or mudslide

Mass Movement in Action

Deposition The “end” stage of the gradational process It is where the weathered material is finally put down or deposited