The Earth's Composition (Daniel Batres)

Seite 1

The composition and structure of the earth

Cores:

The inner core is solid

The outer core is liquid; it also generates the magnetic field

The inner core is solid

The outer core is liquid

The core is mostly iron

Iron nickel alloy both of them

Distance from crust to center of the earth is 6371km (may vary)

Mantle (liquidish)

The mantle is hot and represents 68% of the earth’s mass

More than 82% of the earth’s volume

Upper mantle (the very upper part of it composes the asthenosphere)

Solid, rocky shell

Distance from crust to the bottom of the upper mantle is 660km

The Asthenosphere

The asthenosphere is partially molten upper mantle material that behaves plastically and can flow.

The asthenosphere is the partially molten upper mantle that behaves plastically and can flow, it’s where convection currents occur

Convection currents happen in the asthenosphere

The Lithosphere

The lithosphere is composed of both the crust and the portion of the upper mantle that is solid

Crust and solid upper mantle compose the lithosphere

The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle, rigid solid.

The lithosphere is about 100km thick

Crust: where we live

Two types:

Oceanic: Oceanic crust is made of basaltic rock. Oceanic crust is composed of magma that erupts on the seafloor to create basalt lava flows or cools deeper down to create the intrusive igneous rock gabbro.

Continental: Continental crust is made of granitic rock. Continental crust is made up of many different types of igneous, metamorphic, and sedimentary rocks. The average composition is granite, which is much less dense than the mafic igneous rocks of the oceanic crust.

Densities: Oceanic crust is denser than continental crust although the oceanic crust is thinner than continental crust

Collision: When they collide, the denser crust or the oceanic crust will go below the less dense continental crust

Thickness: Crust’s density varies from 7-70 km

Atmosphere: troposphere, stratosphere, mesosphere, thermosphere, exosphere

Lava comes up because it’s less dense (magma inside the earth, lava on the surface, different terminology)

Harry Hess was an American geologist

and a World War II American Navy officer

who is regarded as one of the "founders"

of the plate tectonics theory.

Plate tectonics

Earth’s lithosphere is broken into slabs of rock

Alfred Wenger first proposed the hypothesis of continental drift in 1915, and he proposed the idea of Pangea

Pangea started spreading 200mil years ago

Continents drifted apart

Wegener’s continental drift hypothesis

He fit south America and Africa together

Fossils match across the seas

Rock types and structures match

Ancient climates

The main objection to Wegener's proposal was its inability to provide a mechanism

Theory of plate tectonics

More encompassing than continental drift,

Associated with earth's rigid outer shell

Called the lithosphere

Consists of several plates

The largest plate is the Pacific plate

Plates are mostly beneath the ocean

Guatemala is influenced by the North American, Caribbean, and Cocos plate

Cocos plate is in the pacific ocean, Guatemala's land, partly is in the Caribbean plate and the rest is in the North American plate

Between the boundary of the North American and Caribbean plate, the Motagua, and Polochic fault are located

The asthenosphere is hotter and weaker than the lithosphere

Allows for the motion of the lithosphere

Convection currents happen in the asthenosphere

Types of plate boundaries:

Divergent plate boundaries;

Two plates move apart

Mantle material upwells to create new seafloor

Ocean ridges and seafloor spreading

Oceanic ridges develop along well

Convergent plate boundaries

Oceanic-continental convergence

Denser oceanic slab sinks into the asthenosphere

Pockets of magma develop and rise

Continental volcanic arc forms

Oceanic-oceanic convergence

Two oceanic slabs converge and one descends beneath the

other

Often forms volcanoes on the ocean floor

Volcanic island arc forms as volcanoes emerge from the sea

Continental-continental convergence

When subducting plates contain continental material, two

continents collide

Transform fault boundaries

Plates slide past one another

No new crust is created or destroyed

Transform faults

Most join two segments of a mid-ocean ridge

Aid the movement of oceanic crustal material

Plates and boundaries migrate and are created and

destroyed

Breakup of Pangea

Formed a new ocean basin- the Atlantic ocean