Earth science geology

Archaean Era3.8 to 2.5 Billion Years Ago • The atmosphere was very different from what we breathe today • The Earth's crust cooled enough that rocks and continental plates began to for

Earth Science

November 12, 2005

Dr Clodfelter

The Geologic Time Scale

The history of the Earth is broken up into a hierarchical set

of divisions for describing geologic time

The Geologic Time Scale, cont.

Highlights of recent fossil finds from

throughout geologic time (from most

ancient to most recent) are:

• Precambrian Era: the first fossil bacteria,

sponges, corals, and algae appear

• Cambrian Period: abundant invertebrate

fossils such as mollusks, crustaceans

The Geologic Time Scale, cont.

• Triassic Period: the first fossils of

primitive dinosaurs appear

• Jurassic Period: the first fossil mammals

and birds; first fossil flowering plants

appear

• Cretaceous Period: large fossil dinosaurs

appear

Tertiary Cretaceous

Jurassic Triassic Permian Carboniferous

Devonian Silurian

Archaean Era

3.8 to 2.5 Billion Years Ago

• The atmosphere was very different from

what we breathe today

• The Earth's crust cooled enough that

rocks and continental plates began to form

• Life first appeared on Earth

– bacteria microfossils

Phanerozoic Eon

543 Million to

• Majority of macroscopic

organisms, fungal, plant

and animals lived

• Appearance of animals

that evolved external

skeletons – like shells –

and animals that formed

internal skeletons – like

vertebrates

Paleozoic Era

543 to 248 Million Years Ago

• In the beginning, multicelled animals

underwent a dramatic "explosion" in

diversity

• At the end, the largest mass extinction in

history wiped out approximately 90% of all marine animal species

Paleozoic Era

543 to 248 Million Years Ago

Mesozoic Era

248 to 65 Million Years Ago

• Mesozoic means "middle animals”

• Lasted 70 Million Years

• Time of transition

• The world-continent of Pangaea existed

• The time in which life as it now exists on

Earth came together

Mesozoic Era

248 to 65 Million Years Ago

Divided into three time

Dinosaurs in the Mesozoic Era

Dinosaurs

– Evolved in the Triassic Period

– Became more diversified in the Jurassic

Period

– Became extinct in the late Cretaceous Period – Fossils of some of the last dinosaurs to walk the Earth can be found in Montana

The Cretaceous/Tertiary Boundary in Montana

Cenozoic Era

• The most recent of the three major

subdivisions of animal history

– The other two are the Paleozoic and the Mesozoic

• Spans only about 65 million years

• Sometimes called the

“Age of Mammals”

A Continental Jigsaw Puzzle: Putting the Pieces Together

• 1911

• German meteorologist

• Alfred Wegener

• theorized that about 300

million years ago all the

continents we know today

were joined together in a

single continent

• he named it “Pangaea”

(pronounced Pan JEE uh)

A Continental Jigsaw Puzzle:

Putting the Pieces Together, cont.

• Wegener suggested that Pangaea split

apart and its pieces began to “drift,” or move away from each other

• He put together his own evidence, as well

as others’, to support his Theory of

Continental Drift

A Continental Jigsaw Puzzle:

Putting the Pieces Together, cont.

• At first, Wegener’s ideas were very popular

because his evidence seemed quite convincing

• Yet a number of observations still remained

unexplained

– What forces caused the continents to move?

• Due to these remaining problems, Wegener’s

theory rapidly lost support and continental drift became “just another theory”

What are Crustal Plates?

• Earth’s crust isn’t one continuous surface

like the skin of an orange

• It is made up of gigantic pieces, like

pieces of a jigsaw puzzle

• Each piece is called a crustal plate

• Some plates form the floor of the oceans

while other carry the continents

Crustal Plates

• Molten rock around the Earth’s core heats

up the mantle above

• Currents of molten rock rise up through

the mantle like boiling water

• As each current hits the underneath of the

crustal plates, it starts to spread out

• This slowly pushes or tears the crust apart

Crustal Plates

• The plates are always on the move

• There are three basic types of plate

boundaries

– where they are sliding past each other

– where plates are separating

– where they are converging (approaching each other)

Crustal Plates

• Spreading Center - the boundary between

separating plates

– Usually found in mid-ocean and are marked by

rugged mountain chains called mid-ocean ridges

• As plates move apart a gap continuously opens

between them

• Molten rock from the earth’s interior flows into

this gap

Plates and Sea Floor Spreading

Crustal Plates

• When plates collide, the force can fold and

thrust upward to form mountains

• Or the force can push the ocean floor

downward to form a deep valley called a

trench

• Here, molten rock can break through the

seabed to form chains of islands like the

The Mariana Trench

The San Andreas Fault

Crustal Plate Activity

Crustal plate activity can…

• Cause earthquakes, volcanic activity, and

tsunamis

• Earthquakes are signs of the great

stresses and which affect the Earth’s crust

• Over a million earthquakes occur every

year

• Tsunamis are giant tidal waves and can

travel at 500 mph!

• Dinosaur Fossil bones have been found in

many different parts of the world

– Further supports Wegener’s single

continent theory

– Different theories as to why

– Most widely accepted is the Big Bang Theory

• Scientists theorize that a meteor hit the

miles per second!)

• Caused a total black out of the sun

• This meteor is believed to have caused

Gulf of Mexico

• The Earth weighs about 6000 million

million million tons

• Two-thirds of the earth is covered by

water

• It would take more than 250 days to walk

around the equator

• Every year, North America and Europe separate

by 3/4ths of an inch

• Scientists predict that life on Earth will only last

50 million more years

Earth = Onion

• Crust – outermost layer, solid rock, but

very thin like skin

• Mantle – denser and heavier than the

crust, inner part of the mantle is described

as “plastic” because it is semi-liquid rock

• Core – outer part is made of molten liquid

rock that is very dense and heavy, “core”

of the core becomes solid and even more

• Forms when rocks deep under the Earth’s

crust melt

• Heat from friction as the rocks rub together

can also form magma

• In places where the Earth’s crust is weak,

magma wells up on the surface as

volcanoes or lava flows

• As it cools, it becomes solid forming

new rock

• Igneous Rock – formed form cooled

magma

• Sedimentary Rock – formed by the

combining together of broken bits of other rocks or sediments

• Metamorphic Rock – changed by

extreme pressure or heat

• Contain complex chemicals called

minerals

• Kinds of Minerals + Size of Crystals =

how the rock was Formed

• Small crystals = rapid cooling

• Large crystals = more lengthy cooling

Ring of Fire

Mount St Helen

Krakatoa, Indonesia

• Volcanic eruption was

heard 3,000 miles

away

• Caused great tidal

wave that killed

perhaps 36,000

people

• Crystals from the

magma are smaller

because they cooled

Crater Lake, Oregon

• The caldera has filled creating one of the

deepest lakes

• It may erupt again

• Made by the action of water and wind as

they laid down like layers of a cake

• Pressure increases and they are warmed

by the heat from deep in the Earth

• Sediment becomes a solid mass of rock

Arbuckle Mountains

Sandstone Limestone

Decaying Plant Material

Peat

• Sea Creature dies and sinks to the sea

bed

• The soft body slowly decays creating oil

with a layer of gas sitting on top

• Skeleton is covered in layers of mud which

gradually become solid rock

• Sea bed rises above sea level

• Radio-active carbon found in all living

things

• Begins to break down after an animal or

plant dies

• By measuring the amount of Carbon – 14

in a fossil, scientists can tell how old it is

• This is called Carbon Dating

• Layer of air surrounding the Earth

• Consists of different kinds and amounts of

gases

– Nitrogen, Oxygen, Carbon Dioxide

• Protects the Earth’s surface

– Filters out harmful radiation from the sun

– Insulates Earth and stops the sun’s heat from

Three Main Layers

1) Ionosphere

• Extends about 50 miles above the surface

• Rarified air

• Temperature gradually rises as you move

away from the Earth

2) Stratosphere

• Extends about 30 miles above the

Earth’s surface

• Contains very little air or water vapor

• Colder than Ionosphere, but warmer than

the Troposphere

3) Troposphere

• Bottom layer

• About 10 miles thick

• Contains nearly all the atmosphere’s air,

water vapor, and clouds

• Temperature gradually drops until is

reaches the stratosphere

• Warm air…

– Lighter and less dense than cold air

– Rises up into the atmosphere

– Produces low pressure

• Cold air…

– Presses down heavily on the Earth’s surface – Produces high pressure

A Meteorologist Measures…

• Air pressure

• Temperature

• Humidity

• Winds speeds and directions

• Precipitation (rain, hail, snow, sleet, fog)

• Cloud types and their heights

– Name used in Asia – Like a tornado and hurricane combined – Rapidly rotating tunnel

of air – Moves over land – Can be 300 miles in diameter

– Winds speed at more than 125 mph

• Similar to cyclones,

but much smaller

• Sometimes only a

mile or so across

The name given to a cyclone which

develops in the western Atlantic Ocean

Infancy Youth Maturity

Alps Rocky Mountains

Arbuckle Mountains Cumberland Mountains

Colorado River Yellowstone River

Rio Grande Red River