Download What is Geology?

A Brief Overview of Major Topics in Geology
Definition
 Geology is the study of the Earth, the materials of
which it is made, the structure of those materials, and
the processes acting upon them.
What Geologist Do?
 Geologists study earth processes: Many processes such
as landslides, earthquakes, floods and volcanic eruptions
can be hazardous to people. Geologists work to understand
these processes well enough to avoid building important
structures where they might be damaged.
 Geologists study earth materials: People use earth
materials every day. They use oil that is produced from
wells, metals that are produced from mines, and water that
has is drawn from streams or from underground.
Geologists conduct studies that locate rocks that contain
important metals, plan the mines that produce them and
the methods used to remove the metals from the rocks.
 Geologists study earth history: Today we are
concerned about climate change. Many geologists are
working to learn about the past climates of earth and
how they have changed across time. This information
is valuable to understand how our current climate is
changing and what the results might be.
Why Should We Care About
Geology?
 What is your car made of?
 What are your houses made of?
 Where do you find diamonds and other precious
stones?
 All of these things are possible because of Geologist
who discovered them.
 “The Farther back you can look, the farther forward
you are likely to see.” -W. Churchill
 What does this question mean to you?
Our Earth
 Our Earth was formed about 4.56 billion years ago!!!
 The earth is divided into four main layers:
 Crust
 Mantle
 Outer Core
 Inner Core
Earth’s Layers: Crust
 Crust: the outermost solid shell of a planet. We live on the
very top of the crust. The crust is the thinnest layer of the
Earth. It floats upon the softer, denser mantle. The Crust is
about 30 miles deep.
 Crust
Crust: Two Types of Crust
 Continental Crust: which forms the continents,
and the areas of shallow seabed close to their
shores, or all the land of the Earth. We live on the
Continental Crust
 Oceanic Crust: is the land beneath all of the
oceans of the Earth. It is much thinner, softer, and
is denser than continental crust.
 Oceanic Crust
Continental Crust
Mantle
 The Mantle is below the Crust. It is about 1,800
miles(2,900 km) thick and makes up nearly 80% of
the Earth's total volume.
 Mantle
Mantle
Upper Mantle: is about 665 miles thick and is made up of molten
material which is a mixture of liquid-like rock. Since it is liquid-like, it
is less dense than solid rock.
Lower Mantle: is about 1357 miles thick and is made up of solid rock
material.
Outer Core
 Traveling still deeper within the Earth, we next would encounter the
Earth’s outer core, which extends to a depth of around 3000 miles
beneath the surface. It is believed that this outer core is made up of
super-heated liquid molten lava. This lava is believed to be mostly iron,
and nickel.
 Outer Core
Inner Core
 Finally, we would reach the Earth’s inner core. The inner
core extends 3,960 miles from Earths surface. It is believed
that this inner core is a solid ball of mostly iron, and nickel.
The Temperature is about 9032 - 10832 ºF (5000-6000
ºC)!!!!
 Inner Core
Plate Tectonics
Continental Drift
 The idea that continents move freely over Earth’s
surface, changing their positions relative to one
another.
 Continents can be made to fit together like pieces of a
picture puzzle like the Atlantic coastlines of Africa and
South America millions of years ago.
 The idea that continents were once joined together
and have split and moved apart from one another has
been around for more than 130 years.
 Pangea
Plate Tectonics
 Definition: The theory that the earth's surface consists of plates, or large
crustal slabs, whose constant motion explains continental drift, mountain
building, volcanoes, etc.
 Earth’s Crust is broken up into plates that move the continents around slowly
over time.
Plate Tectonics: Lithosphere
 Lithosphere: The outer part of the Earth, consisting
of the crust and upper mantle.
 Lithosphere
Plate Tectonics: Asthenosphere
 Asthenosphere: A zone of the earth's mantle that lies
beneath the lithosphere and consists of several
hundred kilometers of deformable rock. The
Asthenosphere is a thick layer of hot rock that is semi
fluid- like.
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Lithosphere
Asthenosphere
 Lithosphere
Asthenosphere
Plate Tectonics
 The Earth’s crust is divided up into “pieces” called
Tectonic Plates which is a massive, irregularly shaped
slab of solid rock, generally composed of both
continental and oceanic lithosphere (crust).
 The lithosphere is solid rock that sits on or “floats”
on top of the semi fluid-like asthenosphere.
 Plate Tectonics shows how these “pieces” of
lithosphere, or crust, move slowly over time and
interact with each other.
Plate Tectonics: Convection
Convection: The cycle of movement in the asthenosphere that causes the
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plates of the lithosphere to move.
Heated material in the asthenosphere becomes less dense and rises toward the
solid lithosphere, through which it cannot rise further.
It therefore begins to move horizontally, dragging the lithosphere along with it
and pushing forward the cooler, denser material in its path.
It is as if the lithosphere is a “floating” floor.
The cooler material eventually sinks down lower into the mantle, becoming
heated there and rising up again, continuing the cycle.
Convection
 Think of convection like boiling a pot of water….
 As water heats to its boiling point, the water rises to
the top and then sinks to the bottom and continues
this cycle.
Plate Tectonics: Ridges and Plate
Boundaries
 Mid-Ocean Ridges: a connected system of undersea volcanoes that roam over
the Earth like the raised string on a baseball. It is a continuous 40,000-mile seam that
encircles Earth and bisects the oceans. A mid-ocean ridge represents an area where, in
accordance with plate tectonic theory, tectonic plates (lithosphere plates) move apart
and new crust is created by magma (molten rock) pushing up from the mantle.
 Mid-Ocean Ridge
 Mid-Ocean Ridge
Ridges and Sea Floor Spreading
 As magma from the asthenosphere rises at mid-ocean
ridges, it creates new crust (or oceanic crust) and causes
the sea floor to spread outward from the ridge. This is
called Sea Floor Spreading.
 A mid ocean ridge is an example of Divergent plate
boundary: locations where plates are moving away from
one another.
What Happens to Old Oceanic
Crust? (Convergent Plate Boundary)
 As mid-ocean ridges slowly creates new lithosphere
(crust), it pushes the existing crust outward towards
the continents.
 Since oceanic crust is softer and more dense than
continental crust, it submerges underneath
continental crust.
 This process is called a Convergent Plate Boundary.
 Convergent plate boundary
Plate Tectonics: Transform Plate
Boundary
 Transform Plate Boundary: locations where two plates
slide past one another.
Plate Boundary Review
 Divergent Plate Boundary
 Convergent Plate Boundary
 Transform Plate Boundary
 http://www.youtube.com/watch?v=Lxq6Vdl0sr4
 A video to help understand plate boundaries and how
they move over millions of years.
Geologic Time
The Earth is about 4.6 billion years old!!!
Geologic Time is divided up into
Eons, Eras, and Periods.
Eras
 Eras: an organized scale that divides the earth's
history into 4 parts
 Precambrian (4.5 billion years ago- 542 million years ago)
 Paleozoic (543 to 248 mya)
 Mesozoic (248 to 65 mya)
 Cenozoic (65 mya to today)
Precambrian Time

Contains 3 Eras within this time period.
1. Hadean Era- (4.5 bya to 3.8 bya) During this time, Earth was
just forming in the Solar system and was made out of gas and dust.
2. Archaean Era- (3.8 bya to 2.5 bya) Earth began to cool and
formed rocks. The atmosphere was very different than it is today. The
air contained many toxic gases that would be very harmful to
humans. The first forms of life appeared during this time which were
in the forms of bacteria.
3. Proterozoic Era- (2.5 bya to 543 mya) During this time,
continents began to form, oxygen began to form in the atmosphere,
and the first fossils appeared which were bacteria life forms.
Precambrian Time
 Precambrian
Paleozoic Era
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Contains 6 Periods within this time.
1.
Cambrian (543 to 490 mya)
Ordovician (490 to 443 mya)
Silurian (443 to 417 mya)
Devonian (417 to 354 mya)
Carboniferous (Mississippian and Pennsylvanian)
(354 to 290 mya)
Permian (290 to 248 mya)
2.
3.
4.
5.
6.
 Paleozoic Era
Mesozoic Era
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Contains 3 Periods within this time.
1.
Triassic (248 to 206 mya)
Jurassic (206 to 144 mya)
Cretaceous (144 to 65 mya)
2.
3.
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During this Era, Dinosaurs were perhaps the most popular
organisms. The began in the Triassic period but were not very diverse
until the Jurassic period. Accept for birds, Dinosaurs became extinct
during the Cretaceous period. Also during this time, the first
flowering plants began.
 Mesozoic Era
Cenozoic Era
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Contains 2 Periods
1.
Tertiary (65 to 1.8 mya)
Quaternary (1.8 mya to today)
2.
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The Cenozoic era is the most recent in geologic time. We are
currently still in the Cenozoic ear (or the Quaternary period). The
Cenozoic spans only about 65 million years ago, from the end of the
Cretaceous and the extinction of dinosaurs to now. The era is also
known as the Age of Mammals because the largest land animals have
been mammals during this time.
 Cenozoic Era
Types of Rocks
Igneous
Metamorphic
Sedimentary
Igneous Rocks
Igneous Rocks
 Igneous Rocks form by crystallization of molten (melted) material;
either magma (within the earth) or lava (on the surface of the earth).
 Igneous rocks are also formed when volcanoes erupt, causing the
magma to rise above the earth's surface. When magma appears above
the earth, it is called lava. Igneous rocks are formed as the lava cools
above ground.
 Underground, they are formed when the melted rock, called magma,
deep within the earth becomes trapped in small pockets. As these
pockets of magma cool slowly underground, the magma becomes
igneous rocks.
Types of Igneous Rocks
 Basalt is a fine-grained, dark-
colored extrusive igneous rock
composed mainly of plagioclase
and pyroxene.
 Diorite is a coarse-grained,
intrusive igneous rock that
contains a mixture of feldspar,
pyroxene, hornblende and
sometimes quartz.
 Granite is a coarse-grained,
light colored, intrusive igneous
rock that contains mainly quartz
and feldspar minerals
Types of Igneous Rock
 Obsidian is a dark-colored
volcanic glass that forms from
the very rapid cooling of molten
rock material. It cools so rapidly
that crystals do not form.
 Rhyolite is a light-colored, finegrained, extrusive igneous rock
that typically contains quartz
and feldspar minerals.
 Welded Tuff is a rock that is
composed of materials that were
ejected from a volcano, fell to
Earth, and then lithified into a
rock. It is usually composed
mainly of volcanic ash and
sometimes contains larger size
particles such as cinders.
Metamorphic Rock
Metamorphic Rock
 Metamorphic Rocks are already existing rocks that
have been altered or molded by lots of pressure, very
hot temperatures, or chemical changes.
 Comes from the word “metamorphism”, which means
"change in form".
Types of Metamorphic Rocks
 Amphibolite is a non-foliated
metamorphic rock that forms
through recrystallization under
conditions of high viscosity and
directed pressure.
 Gneiss is foliated metamorphic
rock that has a banded
appearance and is made up of
granular mineral grains. It
typically contains abundant
quartz or feldspar minerals.
 Marble is a non-foliated
metamorphic rock that is
produced from the
metamorphism of limestone. It
is composed primarily of
calcium carbonate.
Types of Metamorphic Rocks
 Quartzite is a non-foliated
metamorphic rock that is produced
by the metamorphism of sandstone.
It is composed primarily of quartz.
 Schist is metamorphic rock with
well developed foliation. It often
contains significant amounts of
mica which allow the rock to split
into thin pieces. It is a rock of
intermediate metamorphic grade
between phyllite and gneiss.
 Slate is a foliated metamorphic rock
that is formed through the
metamorphism of shale. It is a low
grade metamorphic rock that splits
into thin pieces.
Sedimentary Rocks
Sedimentary Rocks
 Rock that has formed through the deposition and
solidification of earth sediment, especially sediment
transported by water (rivers, lakes, and oceans), ice
(glaciers), and wind. Sedimentary rocks are often deposited
in layers, and frequently contain fossils.
 Sedimentary Rocks form from the remains of other rocks,
earth sand, and other earth materials.
 They are me most common rock type.
 They form over a long period of time and with a lot of
pressure.
Types of Sedimentary Rocks
 Conglomerate is made up of
rounded pebbles cemented
together.
 Sandstone is sand grains
cemented together into solid
stone.
 Limestone is made primarily of
calcium carbonate or calcite.
The most common source of this
calcite is the shells of marine
organisms. The most common
sedimentary rock in the
Bahamas!!
The Rock Cycle