November 12, 2005 Dr. Clodfelter Earth Science November 12, 2005 Dr. Clodfelter

Geologic Time Scale

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

Time and Space Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Precambrian

Precambrian Eon 4.5 Billion to 543 Million Years Ago Nearly 4 thousand million years after the Earth began The first animals left their traces Makes up roughly 7/8 of the Earth's history

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 - Paleozoic rocks are economically important - much of the limestone quarried for building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during this period

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 Important today because of the fossils and oil left behind

Mesozoic Era 248 to 65 Million Years Ago Divided into three time periods: the Triassic (245-208 Million Years Ago) the Jurassic (208-146 Million Years Ago) the Cretaceous (146-65 Million Years Ago)

Dinosaurs in the Mesozoic Era 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 Some of the last dinosaurs to have lived are found in the late Cretaceous deposits of Montana in the United States

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” Chipmunk-like mammal

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

How do the crustal plates move?

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 New crust is continuously formed

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 Hawaiian Islands

The Mariana Trench Example of a trench in the ocean floor Deepest place on earth Located in the Pacific Ocean just off the Mariana Islands near Japan The Kaiko is an unmanned Remotely Operated Vehicle (ROV) The Kaiko first touched down on the bottom of the Pacific Ocean's Mariana Trench in 1995

The San Andreas Fault Forms part of the boundary between the North American Plate and the Pacific Plate

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! Just before an earthquake, dogs howl, chickens flee their roosts, rats leaves their holes, fish leap out of ponds, and wells bubble

Dinosaur Fossils Dinosaur Fossil bones have been found in many different parts of the world Further supports Wegener’s single continent theory The dinosaurs disappeared suddenly Different theories as to why Most widely accepted is the Big Bang Theory

Big Bang Theory Scientists theorize that a meteor hit the Earth at nearly the speed of light (186,000 miles per second!) Caused a total black out of the sun This meteor is believed to have caused the Gulf of Mexico

Gulf of Mexico

Pangaea

Breakup of Pangaea

Earth's Fast Facts 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 dense

Magma 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

Rocks 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

Rocks 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 quickly

Crater Lake, Oregon The caldera has filled creating one of the deepest lakes It may erupt again

Old Faithful and Pagosa Springs

Sedimentary Rock 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

Sedimentary Rock Sandstone Limestone

Decaying Plant Material Peat Coal

How are Fossils Formed? 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 Erosion moves rock covering fossils so they are now exposed on land

Carbon - 14 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

Earth's Atmosphere 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 escaping back into space

Earth's Atmosphere Three Main Layers Ionosphere Extends about 50 miles above the surface Rarified air Temperature gradually rises as you move away from the Earth

Earth's Atmosphere 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

Earth's Atmosphere 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

Air Temperature Warm air… Cold 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

Types of Clouds Cirrus Thin, curly, and wispy shapes Formed in the upper Troposphere Contain ice crystals

Types of Clouds Cumulus Heaped clusters like loose cotton balls Have flat bases and dome shaped tops Sometimes build up into thunder clouds

Types of Clouds Stratus Formed when Cumulus clouds group together to form a continuous layer Grayer in color than Cumulus Bottom of the Stratus layer is in the lower Troposphere

A Meteorologist Measures… Air pressure Temperature Humidity Winds speeds and directions Precipitation (rain, hail, snow, sleet, fog) Cloud types and their heights Visibility

Cyclones 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

Tornadoes Similar to cyclones, but much smaller Sometimes only a mile or so across

Hurricanes The name given to a cyclone which develops in the western Atlantic Ocean Hurricane Francis

Ages of Rivers or Mountains Infancy Youth Maturity Old Age

Mountains in Infancy/Youth Alps Rocky Mountains Left – Alps Right – Rocky Mountains

Mountains in Maturity/Old Age Arbuckle Mountains Cumberland Mountains

Rivers in Infancy/Youth Yellowstone River Colorado River

Rivers in Maturity/Old Age Rio Grande Red River Left – Rio Grande Right – Red River

Geologic Time Scale