Earth Science: Geology - University of Dallas

Earth Science: Geology - University of Dallas

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 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 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 (245208 Million Years Ago) the Jurassic (208146 Million Years Ago) the Cretaceous (146-65 Million Years Ago)

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, Wegeners 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, Wegeners

theory rapidly lost support and continental drift became just another theory What are Crustal Plates? Earths crust isnt 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 Earths 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 earths 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

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 Earths 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 Wegeners single

continent theory The dinosaurs disappeared suddenly Different theories as to why Most widely accepted is the 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 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 Forms when rocks deep under the Earths crust melt Heat from friction as the rocks rub together

can also form magma In places where the Earths 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 quickly 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 Coal 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

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 Earths surface Filters out harmful radiation from the sun

Insulates Earth and stops the suns heat from escaping back into space 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

Earths 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 atmospheres 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 Earths surface Produces high pressure Cirrus Thin, curly, and wispy shapes Formed in the upper

Troposphere Contain ice crystals Cumulus Heaped clusters like loose cotton balls Have flat bases and dome shaped tops

Sometimes build up into thunder 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 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

Old Age Alps Rocky Mountains Arbuckle Mountains

Cumberland Mountains Colorado River Yellowstone River Rio Grande

Red River

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