Mt. KilimanjaroAlexandra Offer

Mt. EtnaMolly Hodson

So…Where do we begin our study of

The Earth ?

The Creation of the Solar SystemBegin with the “Big Bang” approximately 12 billion years ago.Space expanded rapidly and then began to contract.As temperatures cooled, Hydrogen and Helium gases formed.Denser pockets of gas condensed further due to gravity.

Accumulations became galaxies.Began to rotate to form disc-shaped clouds.Center collapsed to form the Sun.As heat increased in the Sun, particles were blown away as “solar wind”.Particles collided and accreted becoming planetesimals.

So how did we get to here?

As larger and larger particles collided,larger planetesimals were formed.Some of these continued to collide andthe largest became the planets, while thesmaller ones may have become moons.

Intense solar radiation heated the closest planets causing the lighter elements to be vaporized and blown out into space.This concentrated the heavier elements like iron and nickel onthe inner planets and the lighter elements on the outer planets.

The Earth’s Earliest History

Beginning of the Earth was extremely violent.Grew by planetesimal impact.Became very hot, heated to the melting point of iron.Innermost rocks began to become compressed, so more heat.Radiogenic heat was added due to radioactive fission.Earth underwent differentiation into layers.

Early Differentiation of the EarthWhat was the Earth’s early composition?

Need to consider meteorites that have struck the earth to get anidea of composition.

Most are iron and nickel.Some contain chondrules.

Small rocky bodies within the meteorites that mayrepresent matter condensing from the original solar nebula.

Earth’s composition should be similar to these meteorites.

However -Meteorites are 35 % iron, while Earth’s surface rocks only 6 %.

Early Differentiation of the Earth

Where did the iron go?

As Earth was still accreting, temperaturerose above melting point of iron.Iron liquified.Because of higher density, iron sank intothe proto-Earth’s center due to gravity.Lighter elements rose to the surface.Originally, Earth was homogeneous.Due to heat and melting, Earth materialsseparated forming concentric zones of differing density.

Thus, Differentiation.

Differentiation and the Earth’s Interior

Earth’s Interior

Three Principal LayersEach has 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

Earth’s Interior

MANTLE - Middle thin layer Density = medium Composition is silicon and oxygen-based but also includes iron and magnesium. Consistency is plastic. Contains two parts, Upper and Lower Mantle.

CORE - Inner layer Density = high Composition is primarily iron and nickel. Contains two parts

Inner core is solid.Outer core is liquid.

Subdivisions of the Earth’s Interior

Within these three principal layers are subdivisions.

Crust consists ofOCEANIC CRUST (brown)CONTINENTAL CRUST (green).

Oceanic crust is thin (8-10 km), dense, and found below ocean basins (blue).Continental crust is thicker(20-70 km), has low density and forms the bulk of continents.

The crust rides on the very upper most portion of the mantle.

The outermost sublayer is the most active geologically.Large scale geological processes occur, includingearthquakes, volcanoes, mountain building and the creation of ocean basins.

Contains parts of the upper mantle and all of the crust.Called the LITHOSPHERE (rock layer).

Lithosphere is a strong layer, but brittle.Represents the outer approximately 100 km of the Earth.Thicker where continents exist, thinner under oceans.

Below the lithosphere resides the ASTHENOSPHERE (weak layer).

Asthenosphere is part of the upper mantle.Asthenosphere is heat softened and acts like a plastic.It is weak, slow flowing, yet solid rock.

(Things that make you go, hmmm.)Generally 100 to 350 km beneath Earth’s surface.

Overlying the lithosphere is the ATMOSPHERE.Composed of gases released during volcanic eruptions and fromplant respiration.

Outgassing from volcanoes also helped produce the water in the Earth’s ocean basins.Led to the initial development of the HYDROSPHERE.Together, the Lithosphere, Atmosphere and Hydrospheresupport the BIOSPHERE.

Atmosphere of the Earth is a thin and fragile layer.

Thermal Energy of the Earth

Heat led to the initial differentiation of the Earth.

Produced core, mantle and crust.

Thermal energy is still being moved from place toplace in the Earth.

Goes from warm to cool areas.

Methods of Thermal Energy Transfer

1. CONDUCTION

Small particles (atoms) get excited by external heat.Vibrate rapidly.Collide with other particles and sets them in motion.

Not an efficient way to move heat in the Earth.

Rock is a very POOR conductor of heat.

2. CONVECTION

Material moves from one place to another, takingheat with it.When Earth got hot enough that parts melted or softened enough to flow, convection occurred.Heat was transferred by rising fluids.Much better method of transferring thermal energy.Rising hot material caused first volcanic eruptions.

Methods of Thermal Energy Transfer

Methods of Thermal Energy Transfer

3. RADIATION

Heated objects radiate energy as well.

Methods of Thermal Energy Transfer

Convection is the most important mechanism for geologic processes.

Rock Types and the Rock Cycle

ROCK - a naturally occurring aggregate of mineralsformed within the Earth.

Delicate Arch, Arches Nat’l Park, UT

Basaltic DikeAcadia Nat’l Park,Maine

A MINERAL is anaturally occurring, inorganic solid, consisting of either a single element or compound,with a definite chemical composition (or varies within

fixed limits),and a systematic internal 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.

IGNEOUS

SEDIMENTARY

METAMORPHIC

Rock Types and the Rock Cycle

Igneous Rocks

- Cooled and solidified from MOLTEN material.- Formed either at or beneath the Earth’s surface.- MELTING of pre-existing rocks required.

Granite

BasalticLava

Sedimentary Rocks

- Pre-existing rocks are weathered and broken downinto fragments that accumulate and are thencompacted or cemented together.

- Also forms from chemical precipitates or organisms.

Metamorphic Rocks

- Form when pre-existing Earth materials are subjectedto heat, pressure and/or chemical reactionsand change the mineralogy, chemicalcomposition and/or structure of the material.

Coal

Gneiss

Slate

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

These changes are reflected in the ROCK CYCLE.