33RRDD.. SSEEMMEESSTTEERR GGRRAADDEE 55 fileAn earthquake is a shaking of the ground caused by the...
Transcript of 33RRDD.. SSEEMMEESSTTEERR GGRRAADDEE 55 fileAn earthquake is a shaking of the ground caused by the...
GGGRRRAAADDDEEE 555 333RRRDDD... SSSEEEMMMEEESSSTTTEEERRR
Plates Rigid blocks of crust and upper mantle rock.
Earthquake A shaking of the ground caused by the sudden release of
energy.
mountains A landform that is much higher than the land around it.
landform Physical (natural) feature on Earth's surface.
volcano A volcano is an opening, or rupture, in Earth's surface or
crust, which allows hot, molten rock, ash, and gases to escape
from below the surface.
crater A large basin formed at the top of the volcano when it fell in
on itself after the eruption
vent A rocky opening in Earth's surface through which magma
flows onto the surface.
Magma molten rock from Earth's mantle
fault A break in the crust along which rock moves.
Weathering The process by which rocks are broken down into smaller
pieces.
Erosion The movement of weathered rocks and soil from one place to
another
Continental drift The theory of how Earth's continents move over its surface.
Seismograph An instrument that records earthquake waves.
deforestation The cutting, clearing, and removal of forest or rainforest
ecosystems.
1
Earth is made up of three layers which are:
1. The crust 2.the mantle 3. the core
Earth's crust is the layer we can walk on.
The crust includes the rock of the ocean floor and large areas of land called
continents
2
Below the crust is the mantle. It is the thickest layer of the planet.
Most of the mantle is solid rock. Some of this layer, though, is partly melted.
This partly melted rock flows slowly like a very thick liquid.
Deep inside Earth is the core.
The core is dense ball made mostly of two metals, iron and nickel.
Earth’s core can be divided into two layers, the inner core and the outer core.
The outer core is a pool of hot, liquid metal.
The inner core is a solid ball made mostly of iron and nickel. It is the hottest
layer of Earth.
Earth's surface is not a single piece of rock. Instead, it is made up of many
plates.
Earth’s crust and upper mantle are broken into continent-sized slabs called
plates. There are 12 major plates in all.
Plates that form the ocean floor are called oceanic plates or oceanic crust.
Plates that form the continents are called continental plates or continental crust.
Continental crust is less dense that oceanic crust.
3
Earth's plates fit together like the pieces of a jigsaw puzzle.
Although these plates are enormous, they actually float on soft rock of the
mantle.
Pressure and heat within the Earth produce currents in the soft rock of the
mantle. As the mantle moves, the plates floating on it move, too.
Plates move very slowly across Earth’s surface on a thin layer of partly melted
mantle.
Most plates move only a few centimeters a year. But because plates are next to
each other, the movement of one plate affects other plates.
Plates can move a way from each other, toward each other, or slide past each
other. As plates move around, they cause great changes in Earth's landforms as
shown in the following table.
4
Plate motion Changes in Earth's landforms
On land On the ocean floor
toward each other
(colliding)
Mountains rise and
volcanoes erupt
e.g. America's Andes
Mountains
Deep trenches form.
Pull apart
Valleys dotted with
volcanoes develop.
e.g. Africa's Great Rift
Ridges and volcanoes form
(This spreading forms new
sea floor at the ridges)
Scrap and slide past
each other Can form earthquakes
Can form earthquakes.
And earthquakes can cause
tsunamis.
Plates move in different
ways
5
Mountain formation
Mountains are the Earth's highest landforms. They form as the crust folds,
cracks, and bends upward because of the movement of Earth's plates.
Many of the highest mountains form where continental plates collide. E.g. the
Himalayas.
At some places, continental and oceanic plates collide. Because continental rock is
less dense than seafloor rock, the continental plate moves up and over the
oceanic plate. E.g. the Cascade Mountain near the Pacific ocean.
Some mountains form where pressure from movement at the boundaries pushes a
block of rock upward. E.g. the Grand Tetons.
6
Plates that pull apart leave gaps between them. Magma bubbles up between the
plates. Magma builds up along the cracks, forming long chains of mountains under
the ocean. These mountains called mid-ocean ridges. E.g. The Mid-Atlantic Ridge.
7
Earthquakes
An earthquake is a shaking of the ground caused by the sudden release of energy
in Earth's crust.
The energy released as plates crush together, scrape past each other, or bend
along jagged boundaries can cause great damage.
Earthquakes also occur along faults in the crust. As Earth's crust can bend or
break in the middle of a plate as forces press in on it. These breaks can form
faults, or places where pieces of the crust move.
8
An earthquake sends out energy in the form of seismic waves.
Seismic waves are like ripples that form on a pond when a stone is tossed in.
Scientists measure and record seismic waves on an instrument called a
seismograph.
Scientists also use numbers to measure earthquakes. The Mercalli
scale measures the movement and damage that an earthquake
causes. The scale uses Roman numerals from I to XII.
We are more familiar with the Richter scale. This scale uses the numbers 1 to 9
to measure the energy an earthquake releases.
A seismograph has two main parts: a pen and a paper-covered rotating drum
For further reading about seismograph visit the following site
http://slohs.slcusd.org/pages/teachers/rhamley/Plate%20Tectonics/seismogra
ph.html
9
Volcanoes
A volcano is a mountain that forms when red-hot melted rock flows through a
crack onto the Earth's
surface.
Melted rock inside Earth is called magma.
Some Effects of Earthquakes
Leave cracks in Earth's
surface
Destroy building and
cities
Cause big sea waves called tsunamis
10
Melted rock that reaches Earth's surface is called lava.
Ways A Volcano Can Form
1-Some volcanoes form in the ocean where plates are moving away from each
other. As the plates move a part, magma slowly rises toward the surface from
deep in the mantle.
When the magma gets to the surface, it cools and hardens to form new ocean
floor.
2- Other volcanoes form where plates are moving toward each other. When a
plate made of ocean crust collide with, or hits, one made of continental crust, the
plate made of ocean crust forced down into the mantle. There it partly melts,
forming magma.
The magma flows onto the surface through a rocky opening called a vent to form
a volcanic mountain
3- Some volcanoes form when a plate moves over a
hot spot in the mantle.
11
Fountains of hot rock punch through the crust to form volcanoes.
The following figure shows the different parts of a volcano
The following figure shows some effects of volcanoes.
Some Effects of volcano
Cover the land with ash and lava
Blow off mountaintops
Send out clouds of ash, rocks, and gases
Can burn nearby areas
N.B. although volcanic eruptions
are often harmful, they can have
good effects on the land around
them. The soil around an active
volcano often has minerals that
help crops grow
12
Continental Drift
Earth's surface has not looked the way it does today.
The surface is constantly changing because of continental drift.
The following diagram summarizes the theory of continental drift.
According to the theory, about 225
million years ago, all of the land on
Earth was joined together in one super
continent called Pangea.
Evidence suggests that about 200 million
years ago, Pangea broke into two big
continents. The southern one, Gondwana and
the northern continent, laurasia.
Earth's surface may look even different
in the future.
13
Evidence supporting continental drift
Fit of the Continents: Noted the similarity in the coastlines of North and
South America and Europe and Africa. Today the fit is done at the continental
shelf and it is nearly a perfect match.
Fossil Similarities: Mesosaurus, reptile similar to modern alligator which lived
in shallow waters of South America and Africa.
Rock Similarities: Rocks of same age juxtaposed across ocean basins.
14
Paleoclimatic Evidence: Glacial deposits at equator / Coral reefs in Antarctica
For further reading about continental drift visit the following web
site
http://geology.csupomona.edu/drjessey/class/Gsc101/Plate.html
Earth's surface also can change due to some forces such as
weathering and erosion. . (Revise Earth and Space summary
for 1st. semester p. 6-8)
15
Some Ways in Which Humans Can Change the Land
Human activities can cause changes to Earth
Some human activities can cause catastrophic changes to Earth's surface as
shown in the following diagram.
Human beings can change the Earth's surface.
Humans make these changes to obtain their needs.
Deforestation is one kind of these changes.
People obtain wood, paper, food, and other resources from the plants and animals
in these forests.
deforestation
Mining resources
buildings
16
Some natural resources found under the Earth's surface such as coal and oil.
To find these resources, humans need to mine them.
Mining can be done in several ways such as digging tunnels deep under the ground,
or scrape away soil and rocks.
Mining also causes changes to the land.
Buildings, roads, houses, and parks around us are built by humans and as such, are
changes to the land.
Human activities also can cause greenhouse effect. (Revise Earth and Space
summary for 1st. semester p. 9-11)
17
Use the terms below to complete the sentences below Weathering Erosion Crust Mantle Core Plate Magma Volcano Earthquake Fault Continental Drift Pangea fossils
1. An …………………….. is a sudden release of energy in Earth's …………….. causing
the ground to shake.
2. A rigid block of Earth's crust and upper mantle rock is a ……………..
3. The remains or traces of past life found in Earth's crust are called…………..
4. Molten rock from Earth's mantle is ………………
5. A …………………. Is a break in Earth's crust, along which pieces of crust move.
6. …………………… is the process of breaking rock into silt, sand, and other tiny
pieces called sediment.
7. Laval is magma that reaches Earth's surface through an opening, called a
…………………….., in Earth's crust.
8. The …………………. Is the layer of rock beneath Earth's crust.
9. The theory that the continents move over Earth's surface is
……………………………….
10. …………………….. is the supercontinent that held all of Earth's land 225 million
years ago.
11. …………………… is the process of moving sediment from one place to another.
12. The …………….. is the center of Earth.
18
Circle the letter of the best choice
13. Gondwana and Laurasia were formed by ……..
A. continental drift B. erosion C. deposition D. earthquake
14. Which of the following is not an ancient continent?
A. Pangea B. Laurasia C. Gondwana D. inner core
15. Scientists use a ………… to measure earthquake waves.
A. lava B. thermometer C. seismograph D. vent
16. A vibration of Earth's crust is an …..
A. earthquake B. plate C. volcano D. flood
17. Most of the magma from a volcano comes up through a rocky opening
called………………..
A. Pangea B. vent C. crater D. inner core
18. Earth's crust and upper mantle are broken into several…………….
A. epicenters B. faults C. plates D. oceans
19. A mountain that forms from lava is a ………
A. continent B. volcano C. Gondwana D. crust
20. The layer of Earth tha is the hottest is the ………
A. mantle B. outer core C. crust D. inner core
19
Answer the following questions
21. What are Earth's three main layers? (illustrate your answer with a labeled
drawing)
22. How fast do Earth's plates move?
23. What are two scales that scientists use to measure earthquakes?
24. What causes and Earthquake?
20
25. How do scientists measure the damage caused by an Earthquake?
26. How do many of the highest mountains form?
27. What is magma and where does it come from?
28. What is deforestation?
21
A B
29. How can humans change the land?
30. What is the difference between weathering and erosion?
31. The following pictures show some changes that are made by humans.
Write the kind of change under each picture.
A
B
C
22