Earth’s Interior and the Rock Cycle

Earth’s Interior

• Four Layers

• Each has a

different

composition

and density

(mass/volume).

CRUST - Outermost layer

• Density = low• Composition is silicon and oxygen-based minerals and rocks. • Crust is extremely thin.• Consistency is rocky.

Composed of two general types.Continental crustOceanic crust

• Oceanic crust is thin (8-10 km), dense, and found below ocean basins.

• Continental crust is thicker(20-70 km), has low density and forms the bulk of continents.

Crust consists of Oceanic Crust (brown) Continental Crust (green).

MANTLE - Middle thin layer

• Density = medium• Composition is silicon and oxygen-based. • Also includes iron and magnesium.• Consistency is plastic.• Two main regions, Upper and Lower Mantle.

Lithosphere (rock layer) - Contains parts of the upper mantle and all of the crust.• Strong layer, but brittle.• Represents outer ~100 km of the Earth.• Thicker where continents exist, thinner under oceans.

Below the lithosphere resides the Asthenosphere (weak layer).

•Heat softened and acts like a plastic.•It is weak, slow flowing, yet solid rock.•Found 100-350 km beneath Earth’s surface.

CORE – Center layers

• Density = high• Composition is primarily iron

and nickel. •Contains two parts

Outer core is liquid. Inner core is solid.

Rock Types and the Rock Cycle

Rock - a naturally occurring aggregate of minerals formed within the Earth.

Delicate Arch, Arches Nat’l Park, UT

Basaltic DikeAcadia Nat’l Park,Maine

A Mineral is/has:1. Naturally occurring 2. An inorganic solid 3. Made of a single element or compound4. Definite chemical composition5. Orderly arrangement of atoms.

Rock Types and the Rock Cycle

DiamondC

PyriteFeS2

BerylBe3Al2(Si6O18)

•Three types of rocks.•These are present in the crust and at the

Earth’s surface.•Each have fundamentally different

origin.

1. Igneous

2. Sedimentary

3. Metamorphic

Rock Types and the Rock Cycle

Igneous Rocks• Cooled and solidified from Molten material.• Formed at or beneath the Earth’s surface.• Melting of pre-existing rocks required.

Granite

BasalticLava

Igneous Rocks – 2 major subdivision

Intrusive Igneous•Formed under ground•Usually medium to coarse grained texture due to slow cooling.•Typically light colored.

Extrusive Igneous•Formed on surface•Glassy or fine-grained due to rapid cooling•May have voids due to degassing of magma•Typically dark colored.

Extrusive (volcanic) Intrusive (plutonic)

Sedimentary Rocks• Pre-existing rocks are weathered and broken into fragments that accumulate. • Are then compacted or cemented together.• Also forms from precipitates or organisms.

Sedimentary Rocks • Formed by the lithification of unconsolidated sediments - compaction and cementation

• The weight of overlying sediments causes sediments to be reduced in volume by 40%.

•Increases pressure and temperature causes some minerals to melt - filling spaces between remaining grains.

•They then harden to form a glue or cement: cementation

Metamorphic Rocks• Form when pre-existing Earth materials are subjected to heat, pressure and/or chemical reactions and change the mineralogy, chemical composition and/or structure of the material.

Coal

Gneiss

Slate

Metamorphic Rocks • Generated by recrystallization of either igneous or sedimentary rocks by the action of any or all of the following:

•Pressure•Temperature•Pore Fluids

• The lower temperature limit is 150 °C. • The upper limit is the melting temperature when magma forms.

• Type of metamorphic rock is determined by the parent rock, and the P/T conditions.

Any rock type can become any other rock type given time and processes acting on them.

These changes are reflected in the ROCK CYCLE.

Here is another version of the Rock Cycle

http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html

The Rock Cycle

Several key processes change rocks:

•Weathering: the physical and chemical breakdown of rock.

•Transportation: the transportation of from

the weathering site

•Deposition: the deposition of sediments after transportation

•Lithification: sediments turning into rock by the processes of compaction and cementation

•Melting: The heating of solid rock till it melts

•Metamorphism: The changing of rock by heat, pressure &chemically active fluids

•Crystallization: The growth of crystals from a cooling magma

•Uplift and exposure: The movement of rock to the surface by weathering & erosion, faulting etc

• http://www.earth2class.org/er/students/256,1,Rocks

• http://www.colby.edu/~bfrueger/141/316,4,Slide 4

• http://sun.menloschool.org/~cfat/powerpoint/earth_science/276,5,Slide 5