CAUSES OF CHANGE: GEOLOGICAL EVOLUTION Objective: Understanding causes and effects of Geological Evolution

Geological Evolution First theory to describe Earth’s mountain ranges was better known as “dried Apple theory”- stated that as the Earth’s surface cooled it did so at unequal rates causes parts to collapse and created mountains. Commonly believed until Alfred Wegner challenged it with his idea of Continental Drift (1911)

Geological Evolution Alfred Wegner noticed that rock and fossil formations on S. America and Africa were very similar. Theorized they were once connected under his idea of Continental Drift Reaction to his idea was skeptical; He could not explain what caused continents to move

Geological Evolution WW II – changes this. The development of Sonar to find enemy submarines discovers that the ocean floor has many features unseen by humans. Largest mountain chain in world Deepest gaps in Earths Surface Brings about theory of Plate Tectonics which restates Wegner’s original ideas

*CAUSES OF CHANGE: GEOLOGICAL EVOLUTION* What causes Geological Evolution/Plate tectonics? Heat from the Earth’s core is the primary reason for the Geological Evolution of the Earth’s Surface. Heat causes convection cells in mantle which cause UNEVEN movement of the Crust

Continental Crust Oceanic Crust Lithosphere Asthenosphere Outer Core Inner Core Lower MANTLE Upper Mantle

*Convection Cells*

*CAUSES OF CHANGE: GEOLOGICAL EVOLUTION* 3 Main Forces of Geological Evolution COMPRESSION is the name of the force which causes Tectonic plates to move toward each other. TENSION is the name of the force which causes the Tectonic plates to move away from each other. SHEARING is the name of the force which causes the plates to move side to side.

CAUSES OF CHANGE: GEOLOGICAL EVOLUTION Common Terms of Geological Evolution: Continental Drift is the theory that the Earth’s land surface drifted over time Plate Tectonics is the theory that says the Earth’s surface is made up of giant plates which move. Fault is the term used to describe a “crack” in the Earth’s surface.

*CAUSES OF CHANGE: * GEOLOGICAL EVOLUTION 3 Types of Plate Boundaries Convergent Boundary is formed when two plates are moving toward each other. If crust is the same type it causes COMPRESSION which causes mountains to form. If crust is different causes SUBDUCTION which causes both mountains and volcanoes to form. These areas are prone to the most violent Earthquakes and Volcanic Eruptions

COMPRESSION

*Subduction*

CAUSES OF CHANGE: *GEOLOGICAL EVOLUTION * Divergent Boundary is formed when 2 plates move away from each other. As a result a Rift Valley forms. These area contain volcanoes and earthquakes but generally are less violent then areas of Convergent Boundaries.

*Rift Valley*

Rift Valley

CAUSES OF CHANGE: *GEOLOGICAL EVOLUTION* Transform Fault Boundary is formed when the 2 plates rub against each other. Area is prone to earthquakes but not volcanoes. The San Andres Fault is a great example of this type of boundary.

San Andres Fault

*CAUSES OF CHANGE:* GEOLOGICAL EVOLUTION Hot Spot Volcanoes are volcanoes which appear in areas where crust is very thin and allows magma to burn through. Creates a chain of island as plate moves hot area. Hawaii is an example.

Hot Spot Volcanoes