Mt. Kilimanjaro
Alexandra Offer
Mt. Etna
Molly Hodson
So…
Where do we begin our study of
The Earth ?
The Creation of the Solar System
Begin 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 discshaped 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 and
the largest became the planets, while the
smaller 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 on
the 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 Earth
What was the Earth’s early composition?
Need to consider meteorites that have struck the earth to get an
idea of composition.
Most are iron and nickel.
Some contain chondrules.
Small rocky bodies within the meteorites that may
represent 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, temperature
rose above melting point of iron.
Iron liquified.
Because of higher density, iron sank into
the proto-Earth’s center due to gravity.
Lighter elements rose to the surface.
Originally, Earth was homogeneous.
Due to heat and melting, Earth materials
separated forming concentric zones of
differing density.
Thus, Differentiation.
Differentiation and the Earth’s Interior
Earth’s Interior
Three Principal Layers
Each 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 crust
Oceanic 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 of
OCEANIC 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, including
earthquakes, 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 from
plant 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 Hydrosphere
support 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 to
place 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.
Methods of Thermal Energy Transfer
2. CONVECTION
Material moves from one place to another, taking
heat 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
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 minerals
formed within the Earth.
Basaltic Dike
Acadia Nat’l Park,
Maine
Delicate Arch, Arches Nat’l Park, UT
Rock Types and the Rock Cycle
A MINERAL is a
naturally 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.
Pyrite
FeS2
Diamond
C
Beryl
Be3Al2(Si6O18)
Rock Types and the Rock Cycle
Three types of rocks.
These are present in the crust and at the
Earth’s surface.
Each have fundamentally different origin.
IGNEOUS
SEDIMENTARY
METAMORPHIC
Igneous Rocks
- Cooled and solidified from MOLTEN material.
- Formed either at or beneath the Earth’s surface.
- MELTING of pre-existing rocks required.
Granite
Basaltic
Lava
Sedimentary Rocks
- Pre-existing rocks are weathered and broken down
into fragments that accumulate and are then
compacted or cemented together.
- Also forms from chemical precipitates or organisms.
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.
Gneiss
Coal
Slate
Any rock type can become any other rock type given time and
processes acting on them.
These changes are reflected in the ROCK CYCLE.