Transcript Journey to the Center of Earth

Center Of The
Earth
The Earth The Earth formed about 4.6 billion years ago as bits of
material collided and stuck together. The planet grew
larger as more and more material was added. These
impacts, along with the Earth’s gravity, produced intense
heat. The young planet became a glowing ball of melted
rock.
In time, denser materials, such as iron and nickel, sank
toward the center of Earth. Less dense materials moved
toward the surface. Other materials settled between the
planet’s center and its surface. Slowly, Earth’s main layers
formed—the core, the mantle, and the crust.
Layers of the Earth
•
•
•
•
Crust
Mantle
Outer Core
Inner Core
Earth’s interior layers.
• The layers of the
Earth consist of the
crust, mantle, outer
core and inner core.
Crust
• This is the layer that we live on.
• The thickness ranges from 6 kilometers
to 70 kilometers.
• It consists of cooler rock. It’s
temperature is 0 degrees – 700 degrees
Celsius.
• It is the thinnest layer of the earth
THE CRUSTAL SURFACE.
• CONTINENTAL CRUST –
This is between 20 and 60
km thick. It is composed of
granitic rocks.
• OCEANIC CRUST This is only about 10 km
thick. It is composed of
basaltic rocks.
The Mantle
• The mantle is semi- liquid. This layer consists of
magnesium, iron, and silicon.
• The mantle is Earth’s thickest layer. It is 2900 km
thick.
• It’s temperature is 870 degrees – 4,400 degrees
Celsius.
• Flow in the mantle occurs as convection currents;
hot material in the mantle rises up, cools down, and
then sinks.
The Outer Core
• The temperature here is very high, so iron and nickel are present
in a liquid state.
• The molten outer core flows at a very slow rate.
• This layer has electrical current which powers the Earth’s
magnetic field.
• The outer core is 2300 km thick.
• Its temperature is 4,400 degrees – 6,100 degrees Celsius.
The Inner Core
• This layer is solid.
• The inner core consists of the metals, nickel
and iron.
• Its temperature is 7,000 degrees – 8,000
degrees Celsius.
• It is 2,400 km thick.
Composition of the Earth.
40%
iron
oxygen
30%
20%
10%
0%
silicon magnesium
the other
Lithosphere and Asthenosphere
Earth’s crust and the very top of the mantle
together form the Lithosphere. This layer is the
most rigid of all the layers. The lithosphere sits
on top of the Asthenosphere, a layer of hotter,
softer rock in the upper mantle. This layer is soft
enough to flow slowly like hot tar.
Lithosphere – The solid part of the Earth, consisting
of the crust and the upper mantle.
Tectonic Plates The lithosphere does not form a continuous
shell around Earth but is broken into many
large and small slabs of rock called Tectonic
Plates. Tectonic plates fit together like a jigsaw
puzzle that makes up the surface of the Earth.
Most large tectonic plates include both
continental crust and oceanic crust. Most of the
thicker continental crust rises above the ocean.
The rest of the plate is thin oceanic crust, or sea
floor, and is underwater.
Tectonic Plates - The tectonic plates of the world
were mapped in the second half of the 20th century.
THE THEORY OF PLATE TECTONICS
• This theory explains how
and why the surface of the
earth constantly changes.
• This theory states that the
earth’s outer shell, the
lithosphere is divided into
large plates.
• Each plate moves as a
single unit so the interiors
of the plates are generally
stable. Major activities like
earthquakes or volcanoes
occur along the plate
boundaries.
Continental Drift In the late 1800s, German scientist Alfred
Wegener proposed a hypothesis known as
continental drift suggesting that the Earth’s
continents were once joined in a single
landmass and gradually drifted, apart. In the
mid-1900s scientists found new evidence that
supported continental drift.
Evidence for Continental Drift Fossils - Wegener learned that the fossils of an
ancient reptile, Mesosaurus had been discovered
in South America and western Africa. This small
reptile lived about 270 million years ago. Its
fossils were not found anywhere else in the world.
Wegener said this fact could easily be explained if
South America and Africa were once joined.
Evidence for Continental Drift Climate - Evidence of climate change supported
Wegener’s hypothesis. Greenland lies near the
Arctic Circle and is mostly covered in ice. Yet
fossils of tropical plants can be found on its
shores. In contrast, South Africa today has a warm
climate. Yet its rocks were deeply scratched by ice
sheets that once covered the area.
Evidence for Continental Drift Geology - Wegener’s best evidence for
continental drift came from the kinds of
rocks that make up the continents. He
showed that the type of rock found in Brazil
matched the rock found in western Africa.
Also, limestone layers in the Appalachian
Mountains of North America were exactly
like the limestone in Scotland’s Highlands.
Pangaea – The Super Continent For Wegener, all the evidence pointed to a
single conclusion. The continents had once
been joined in a huge supercontinent he
called Pangaea. This giant continent
reached from pole to pole and was centered
over the area where Africa lies today.
Pangaea began to split apart some 200
million years ago. In time, the continents
moved to where they are today.
The Theory of Plate Tectonics This theory states that Earth’s lithosphere is made
up of huge plates that move over the surface of the
Earth.
DIFFERENT TYPES OF PLATE BONDARIES
A.
B.
C.
DIVERGENT PLATE
BOUNDARIES- Plates are moving
away from each other. Very active
volcanically due to the rising of
magma. (Mid-Atlantic Ridge)
CONVERGENT PLATE
BONDARIES- Plates are coming
together. The regions of plate collision
are regions of great mountain
buildings. (Andes, Himalayas, Sierra
Nevada)
TRANSFORM BOUNDARIES – Two
tectonic plates scrape past each other
and crust is neither formed nor
destroyed. (San Andreas Fault in
California)
Sea Floor Spreads apart at Divergent Boundaries:
Mid-Ocean Ridges and Rift Valleys are formed
The Mid-Atlantic Ridge – The World’s longest MidOcean Ridge, runs the length of the Atlantic Ocean!
Three Types of Convergent Boundaries -
1) Where Two Continental Plates Meet
2) Where Two Oceanic Plates Meet
3) Where One Oceanic Plate meets with a
Continental Plate
Plates Push Together at Convergent
Boundaries
1) When Two plates with Continental Crust
collide they will crumple and fold the rock
between them.
2) Plates with older, denser Oceanic Crust
will sink beneath another plate. When one
plate sinks beneath another, it is called
“Subduction”.
• Oceanic–Oceanic Subduction:
Collision between two oceanic plates can
result in the process when one plate bends
and sinks beneath the other to produce
deep oceanic trenches. (Mariana Trench)
• Oceanic–Continental Subduction:
When an oceanic plate and a continental
plate converge, the denser oceanic plate is
subducted beneath the less dense
continental plate. A deep-ocean trench is
formed and magma is generated. (Andes)
• Continental–Continental Collision:
When two continental plates collide their
edges crumple and fold forming folded
mountains. The collision between
continental plates has produced some of
the most famous mountain ranges.
(Himalayas, European Alps, Appalachian)
Deep Ocean Trenches Trenches are like deep canyons that form in
the ocean floor as a plate sinks. The deepest
known trench is the Mariana Trench, which
is the deepest place in the world’s oceans,
extending nearly 11,000 meters into the sea
floor. Most deep-ocean trenches are found
in the Pacific Ocean.
Island Arcs – These are chains of volcanic islands that form
on the top plate, parallel to a deep-ocean trench.
Transform Boundaries -
San Andreas Fault – This is a Transform Boundary that
runs from the Gulf of California through the San Francisco
area.
Theory of plate Tectonics The theory of Plate Tectonics has changed
the way that scientists view Earth. Today,
the theory helps them to explain Earth’s past
and to predict what might happen along
plate boundaries in the future and also
predict other geological events.
MINERALS
Minerals have four qualities ;
• Formed in nature
• Are solids
• Have a definite chemical makeup
• Have a crystal structure (crystals are solids
in which the atoms are arranged in an
orderly, repeating 3-D pattern.)
Properties Of Minerals:
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Color
Streak
Luster
Cleavage
Fracture
Density
Hardness
Moh’s Scale:
Hardness
1
2
3
4
5
6
7
8
9
10
Mineral
Talc
Gypsum
Calcite
Fluorite
Apatite
Feldspar
Quartz
Topaz
Corundum
Diamond
Special properties of Minerals:
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Fluorescence - Fluorite
Magnetic - Magnetite
Radioactive
Minerals in the carbonate group, such as
calcite, react with acid.
Formation Of Minerals:
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•
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When water evaporates - Halite
When hot water cools down – Gold
Molten rock cools – Quartz
Heat and pressure cause changes – Graphite
Organisms produce minerals – Calcite and
Apatite
Mining of Minerals :
• Surface Mining – 1) Panning
2) Strip Mining
3) Open-pit Mining
• Deep Mining
ROCK FORMING MINERALS:
There are thousands of different minerals on
Earth but only about 30 are common in the
Earth’s crust. These 30 minerals make up
most of the rocks in the crust. They are
called the rock-forming minerals.
Groups of Minerals
• Silicates - These contain oxygen and silicon—the
two most common elements in Earth’s crust. They
make up 90% of the rocks in the Earth’s crust.
Some examples are - Quartz, feldspar, and mica
• Carbonates - These contain carbon and oxygen
joined together. Example - Calcite, found in
seashells
• Oxides – These consist of an element, usually
a metal, joined to oxygen. Example –
hematite, which is a source of iron.
Elements
Elements are substances which are made
up of the same kinds of atoms.
Of the known 112 elements, 92 occur
naturally in the earth’s crust and
combine to make 4000 different minerals.
MINERALS
Silicates
Nonsilicates
Clay Minerals
Ferromagnesian
Carbonates
Sulfates
Oxides
Sulfides
Phosphates
Halides
Nonferromagnesians
Native Elements
ROCKS AND MINERALS
• A ROCK is a naturally formed solid, that is usually
made up of one or more types of minerals.
• A MINERAL is a substance that forms in nature, is a
solid, has a definite chemical makeup, and has a crystal
structure.
TYPES OF ROCKS:
• IGNEOUS ROCKS
• SEDIMENTARY ROCKS
• METAMORPHIC ROCKS
IGNEOUS ROCKS
IGNEOUS ROCKS are formed by the
cooling and crystallization of hot, molten
rock – magma. The word igneous means
“formed by fire”. Igneous rocks make up
about 95% of the Earth crust. Basalt and
granite are common igneous rocks.
SEDIMENTARY ROCKS
SEDIMENTARY ROCKS are formed from
pieces of other rocks (sediments) carried by
water, wind, or ice. Sedimentary rocks are
easy to find on the ground beneath our feet
– the uppermost portion of Earth crust.
Sedimentary rocks cover more than twothirds of the Earth’s surface. Sandstone,
shale, and limestone are common
sedimentary rocks.
METAMORPHIC ROCKS
METAMORPHIC ROCKS are formed from older,
preexisting rocks (igneous, sedimentary, or
metamorphic) that are transformed by high
temperature, high pressure, or both – without
melting. The word metamorphic means “changed in
form”. Marble and slate are common metamorphic
rocks.
ROCK CYCLE
Activity # 1- Making a
Cross Section
• Identify the layers of the
earth (crust, mantle, outer
core, and inner core).
• Draw an apple
• Identify the skin (crust)
• Identify the apple (mantle)
• Identify the outside of the
seeds (outer core).
• Identify the inside of the
seeds (inner core).
Activity #2- Making Flash
Cards
• Read the book “Magic
School Bus- Inside the
Earth.”
• Make a list of the earth’s
characteristics.
• Get into groups of four.
• Make flash cards using the
information form the
book.
• Quiz each other and see
who gets the most correct.
Activity #3- Making a
Model of the Earth
• Review the
characteristics of the
layers of the earth.
• Choose four facts that
you wish to discuss.
• Make a poster of the
earth, its layers, and
the information that
you chose.
Assessment
• Have students present
his/her poster or earth
creation.
• Grade them on the
responses to the
flashcards.
• Play a game that involves
questions about the crust,
mantle, outer core, and
inner core.