Geology - Plate Tectonics

Earth's layers were formed by

Differentiation and is based on density, composition, temperature, and pressure

Components of the Earth's Crust

Inner Core, Outer Core, Mantle, and Lithosphere

Lithosphere

made of crust and upper part of mantle; broken into tectonic plates

Astenosphere

Hotter and denser and located below the lithosphere, allows for the movement of plates through mantle convection

Oceanic Crust

Apart of the lithosphere which is thinner, younger, and denser

Continental Cust

Apart of the lithosphere which is thicker, older, and less dense

What is Plate Tectonic Theory?

A unifying theory that provides the framework for understanding processes operating within the Earth's interior and surface.

Alfred Wegener

A German scientist who proposed the theory of continental drift in 1915

Continental Drift Theory

Alfred Wegener believed landmasses of Earth once fit together to form single landmass called "Pangaea"; landmasses "drifted" to where they are today over 200 million years ago

Name of Wegener's supercontinent

Pangaea

Why was Wegener's theory rejected?

There was no mechanism to prove his theory and he was a meteorologist

Evidence for Continental Drift

1. the continental fit of Africa and South America, 2. Fossils match across the seas, 3. Ancient Climates, 4. Rock type and structure match

Describe how mantle convection moves lithospheric plates (continents)

The Earth's heat drives convection currents and mantle plumes extend from mantle-core boundaries as it has less density than solid rock

Harry Hess

Proposed the theory of sea-floor spreading in 1960, provided a mechanism which surpassed Wegener's.

Sea-floor spreading

the process by which new oceanic crust forms as magma rises toward the surface and solidifies. Older rock is pushed away in opposite directions

Sea-floor spreading creates

mid-ocean ridges, rift valleys, and ocean basins

How does Sea-floor spreading relate to mid-oceanic ridge systems

Magma rises at mid-ocean ridges as tectonic plates rise up to create new crust

Where are the youngest and oldest oceanic crusts along mid-oceanic ridge systems

The youngest is located at the center, and the oldest is spread farthest from the oceanic ridge

Three types of boundaries are

convergent, divergent, transform

convergent boundary

A destructive plate boundary where two plates move toward each other.

What do convergent boundaries form?

Mountains, Volcanic Arcs, and Trenches

The three types of convergent boundaries

oceanic-oceanic, oceanic-continental, continental-continental

What happens when 2 oceanic plates collide?

Ocean trenches form as the denser oceanic plate subducts.

What is formed as a result of oceanic-oceanic plate subduction?

Ocean volcanoes.

How are volcanic islands formed in oceanic-oceanic collisions?

Volcanoes emerge from the sea.

Examples of Oceanic-Oceanic Convergence

Aleutian Mountains, Mariana Trench, and Tonga Islands

What happens during oceanic-continental subduction?

Oceanic crust subduces below continental crust and partially melts.

What rises from continental volcanic arcs during oceanic-continental subduction?

Molten rock rises from continental volcanic arcs near the coastline.

Where are continental volcanic arcs located in relation to oceanic-continental trenches?

Continental volcanic arcs are parallel to ocean trenches. (Ex: Andes Mountains and Peru-Chile Trench)

continental-continental convergence

Begins as subduction, 2 plates collide after ocean basins close. (Ex: Himalayas and Alps Mountains)

divergent boundary

A constructive margin where 2 plates move apart and mantle material rises to form new crust

transform boundary

A plate boundary where two plates move past each other in opposite directions. No new crust is created/destroyed, and no new crust is formed

2 types of transform boundaries

oceanic and continental

Japan's plate boundary

Convergent

Cascade Range Plate Boundary

Convergent

San Andreas Fault Boundary

Transform

Himalayas Boundary

Convergent

Aluetion Islands

Convergent

Boundary that was responsible for the breakup of Pangea?

Divergent

Plate boundaries that cause earthquakes

All (Convergent, Divergent, and Transform)

Plate boundary that causes deep-focus earthquakes

Convergent

Plate boundaries associated with trenches and volcanic arcs

Convergent

The 2 types of volcanic arcs

Continental and Island

How do continental volcanic arcs form?

When oceanic crust subducts below continental plates, creating a subduction zone. Arcs are formed near the coastline

How do volcanic islands form?

oceanic-oceanic convergence, the denser plate subducts and partially melts and produces magma

Significance of the ring of fire

The world's most volcanically and seismically active zone, responsible for ~75% of volcanoes and ~90% of all earthquakes, due to the constant movement of tectonic plates

What causes offsets along the mid-oceanic ridge system?

Tectonic plates pulling apart at divergent boundaries in a process called seafloor spreading

What type of plate boundary seldom produces volcanoes?

Transform