earth makalah

8/4/2019 Earth Makalah

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Earth is the third planet from the Sun and the fifth largest:

orbit: 149,600,000 km (1.00 AU) from Sun

diameter: 12,756.3 km

mass: 5.972e24 kg

Earth is the only planet whose English name does not derive from Greek/Roman mythology. The

name derives from Old English and Germanic. There are, of course, hundreds of other names for

the planet in other languages. In Roman Mythology, the goddess of the Earth was Tellus - the fertile

soil (Greek: Gaia, terra mater - Mother Earth).

It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth

is just another planet.

Earth's Plate Boundaries delineated by earthquake epicenters

Earth, of course, can be studied without the aid of spacecraft. Nevertheless it was not until the

twentieth century that we had maps of the entire planet. Pictures of the planet taken from space are

of considerable importance; for example, they are an enormous help in weather prediction and

especially in tracking and predicting hurricanes. And they are extraordinarily beautiful.

The Earth is divided into several layers which have distinct chemical and seismic properties (depths

in km):

0- 40 Crust

40- 400 Upper mantle

400- 650 Transition region

650-2700 Lower mantle

2700-2890 D'' layer

2890-5150 Outer core

5150-6378 Inner core

The crust varies considerably in thickness, it is thinner under the oceans, thicker under the

continents. The inner core and crust are solid; the outer core and mantle layers are plastic or semi-

fluid. The various layers are separated by discontinuities which are evident in seismic data; the best


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known of these is the Mohorovicic discontinuity between the crust and upper mantle.

Most of the mass of the Earth is in the mantle, most of the rest in the core; the part we inhabit is a

tiny fraction of the whole (values below x10^24 kilograms):

atmosphere = 0.0000051

oceans = 0.0014

crust = 0.026

mantle = 4.043

outer core = 1.835

inner core = 0.09675

The core is probably composed mostly of iron (or nickel/iron) though it is possible that some lighter

elements may be present, too. Temperatures at the center of the core may be as high as 7500 K,

hotter than the surface of the Sun. The lower mantle is probably mostly silicon, magnesium andoxygen with some iron, calcium and aluminum. The upper mantle is mostly olivene and pyroxene

(iron/magnesium silicates), calcium and aluminum. We know most of this only from seismic

techniques; samples from the upper mantle arrive at the surface as lava from volcanoes but the

majority of the Earth is inaccessible. The crust is primarily quartz (silicon dioxide) and other

silicates like feldspar. Taken as a whole, the Earth's chemical composition (by mass) is:

South America by Galileo

34.6% Iron

29.5% Oxygen

15.2% Silicon

12.7% Magnesium

2.4% Nickel

1.9% Sulfur

0.05% Titanium

The Earth is the densest major body in the solar system.

The other terrestrial planets probably have similar structures and compositions with some

differences: the Moon has at most a small core; Mercury has an extra large core (relative to its

diameter); the mantles of Mars and the Moon are much thicker; the Moon and Mercury may not

have chemically distinct crusts; Earth may be the only one with distinct inner and outer cores. Note,

however, that our knowledge of planetary interiors is mostly theoretical even for the Earth.

Unlike the other terrestrial planets, Earth's crust is divided into several separate solid plates which

float around independently on top of the hot mantle below. The theory that describes this is known

as plate tectonics. It is characterized by two major processes: spreading and subduction. Spreading

occurs when two plates move away from each other and new crust is created by upwelling magma


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from below. Subduction occurs when two plates collide and the edge of one dives beneath the other

and ends up being destroyed in the mantle. There is also transverse motion at some plate boundaries

(i.e. the San Andreas Fault in California) and collisions between continental plates (i.e.

India/Eurasia). There are (at present) eight major plates:

North American Plate - North America, western North Atlantic and Greenland Earth's Plate

Boundaries delineated by earthquake epicenters

South American Plate - South America and western South Atlantic

Antarctic Plate - Antarctica and the "Southern Ocean"

Eurasian Plate - eastern North Atlantic, Europe and Asia except for India

African Plate - Africa, eastern South Atlantic and western Indian Ocean

Indian-Australian Plate - India, Australia, New Zealand and most of Indian Ocean

Nazca Plate - eastern Pacific Ocean adjacent to South AmericaPacific Plate - most of the Pacific Ocean (and the southern coast of California!)

There are also twenty or more small plates such as the Arabian, Cocos, and Philippine Plates.

Earthquakes are much more common at the plate boundaries. Plotting their locations makes it easy

to see the plate boundaries.

The Earth's surface is very young. In the relatively short (by astronomical standards) period of

500,000,000 years or so erosion and tectonic processes destroy and recreate most of the Earth's

surface and thereby eliminate almost all traces of earlier geologic surface history (such as impact

craters). Thus the very early history of the Earth has mostly been erased. The Earth is 4.5 to 4.6

billion years old, but the oldest known rocks are about 4 billion years old and rocks older than 3

billion years are rare. The oldest fossils of living organisms are less than 3.9 billion years old. There

is no record of the critical period when life was first getting started.

Space Shuttle view of the Strait of Gibraltar

71 Percent of the Earth's surface is covered with water. Earth is the only planet on which water can

exist in liquid form on the surface (though there may be liquid ethane or methane on Titan's surface

and liquid water beneath the surface of Europa). Liquid water is, of course, essential for life as we

know it. The heat capacity of the oceans is also very important in keeping the Earth's temperature

relatively stable. Liquid water is also responsible for most of the erosion and weathering of the

Earth's continents, a process unique in the solar system today (though it may have occurred on Mars


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in the past).

Earth's atmosphere seen at the limbThe Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and

water. There was probably a very much larger amount of carbon dioxide in the Earth's atmosphere

when the Earth was first formed, but it has since been almost all incorporated into carbonate rocks

and to a lesser extent dissolved into the oceans and consumed by living plants. Plate tectonics and

biological processes now maintain a continual flow of carbon dioxide from the atmosphere to these

various "sinks" and back again. The tiny amount of carbon dioxide resident in the atmosphere at any

time is extremely important to the maintenance of the Earth's surface temperature via the

greenhouse effect. The greenhouse effect raises the average surface temperature about 35 degrees C

above what it would otherwise be (from a frigid -21 C to a comfortable +14 C); without it the

oceans would freeze and life as we know it would be impossible. (Water vapor is also an important

greenhouse gas.)

The presence of free oxygen is quite remarkable from a chemical point of view. Oxygen is a very

reactive gas and under "normal" circumstances would quickly combine with other elements. The

oxygen in Earth's atmosphere is produced and maintained by biological processes. Without life

there would be no free oxygen.

The interaction of the Earth and the Moon slows the Earth's rotation by about 2 milliseconds per


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century. Current research indicates that about 900 million years ago there were 481 18-hour days in

a year.

Earth has a modest magnetic field produced by electric currents in the outer core. The interaction of

the solar wind, the Earth's magnetic field and the Earth's upper atmosphere causes the auroras (see

the Interplanetary Medium). Irregularities in these factors cause the magnetic poles to move and

even reverse relative to the surface; the geomagnetic north pole is currently located in northern

Canada. (The "geomagnetic north pole" is the position on the Earth's surface directly above the

south pole of the Earth's field.)

The Earth's magnetic field and its interaction with the solar wind also produce the Van Allen

radiation belts, a pair of doughnut shaped rings of ionized gas (or plasma) trapped in orbit around

the Earth. The outer belt stretches from 19,000 km in altitude to 41,000 km; the inner belt lies

between 13,000 km and 7,600 km in altitude.Earth's Satellite

Earth has only one natural satellite, the Moon. But

thousands of small artificial satellites have also been placed in orbit around the Earth.

Asteroids 3753 Cruithne and 2002 AA29 have complicated orbital relationships with the Earth;

they're not really moons, the term "companion" is being used. It is somewhat similar to the situation

with Saturn's moons Janus and Epimetheus.

Lilith doesn't exist but it's an interesting story.

Distance Radius Mass

Satellite (000 km) (km) (kg)

--------- -------- ------ -------

Moon 384 1738 7.35e22


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What is the greenhouse effect?

There are two meanings of the term "greenhouse effect". There is a "natural" greenhouse effect that

keeps the Earth's climate warm and habitable. There is also the "man-made" greenhouse effect,

which is the enhancement of Earth's natural greenhouse effect by the addition of greenhouse gases

from the burning of fossil fuels (mainly petroleum, coal, and natural gas).

In order to understand how the greenhouse effect operates, we need to first understand "infrared

radiation". Greenhouse gases trap some of the infrared radiation that escapes from the Earth,

making the Earth warmer that it would otherwise be. You can think of greenhouse gases as sort of a

"blanket" for infrared radiation-- it keeps the lower layers of the atmosphere warmer, and the upper

layers colder, than if the greenhouse gases were not there.

About 80-90% of the Earth's natural greenhouse effect is due to water vapor, a strong greenhouse

gas. The remainder is due to carbon dioxide, methane, and a few other minor gases.

It is the carbon dioxide concentration that is increasing, due to the burning of fossil fuels (as well

as from some rainforest burning). This is the man-made portion of the greenhouse effect, and it is

believed by many scientists to be responsible for the global warming of the last 150 years.


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Also, the concentration of methane, although small, has also increased in recent decades. The

reasons for this increase, though, are uncertain.

Three Parts of Earth's Interior: A knowledge of earth's interior is essential for understanding plate

tectonics. A good analogy for teaching about earth's interior is a piece of fruit with a large pit such

as a peach or a plum. Most students are familiar with these fruits and have seen them cut in half. In

addition the size of the features are very similar.

If we cut a piece of fruit in half we will see that it is composed of three parts: 1) a very thin skin, 2)

a seed of significant size located in the center, and 3) most of the mass of the fruit being contained

within the flesh. Cutting the earth we would see: 1) a very thin crust on the outside, 2) a core of

significant size in the center, and 3) most of the mass of the Earth contained in the mantle.

Earth's Crust: There are two different types of crust: thin oceanic crust that underlies the ocean

basins and thicker continental crust that underlies the continents. These two different types of crust

are made up of different types of rock. The thin oceanic crust is composed of primarily of basalt and

the thicker continental crust is composed primarily of granite. The low density of the thick

continental crust allows it to "float" in high relief on the much higher density mantle below.

Earth's Mantle: Earth's mantle is thought to be composed mainly of olivine-rich rock. It has

different temperatures at different depths. The temperature is lowest immediately beneath the crust

and increases with depth. The highest temperatures occur where the mantle material is in contact

with the heat-producing core. This steady increase of temperature with depth is known as the

geothermal gradient. The geothermal gradient is responsible for different rock behaviors and the

different rock behaviors are used to divide the mantle into two different zones. Rocks in the upper

mantle are cool and brittle, while rocks in the lower mantle are hot and soft (but not molten). Rocks

in the upper mantle are brittle enough to break under stress and produce earthquakes. However,

rocks in the lower mantle are soft and flow when subjected to forces instead of breaking. The lower

limit of brittle behavior is the boundary between the upper and lower mantle.

Earth's Core: Earth's Core is thought to be composed mainly of an iron and nickel alloy. Thiscomposition is assumed based upon calculations of its density and upon the fact that many


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meteorites (which are thought to be portions of the interior of a planetary body) are iron-nickel

alloys. The core is earth's source of internal heat because it contains radioactive materials which

release heat as they break down into more stable substances.

The core is divided into two different zones. The outer core is a liquid because the temperatures

there are adequate to melt the iron-nickel alloy. However, the inner core is a solid even though its

temperature is higher than the outer core. Here, tremendous pressure, produced by the weight of the

overlying rocks is strong enough to crowd the atoms tightly together and prevents the liquid state.

History of Plate tectonics

Plate tectonic theory had its beginnings in 1915 when Alfred Wegener proposed his theory of

"continental drift." Wegener proposed that the continents plowed through crust of ocean basins,which would explain why the outlines of many coastlines (like South America and Africa) look like

they fit together like a puzzle. Wegener was not the first to notice this puzzle-like fit of the

continents (Magellan and other early explorers also noticed this on their maps), but he was one of

the first to realize that the Earth's surface has changed through time, and that continents that are

separated now may have been joined together at one point in the past.

Paleontologists had also found that there were fossils of similar species found on continents that are

now separated by great geographic distance. Paleoclimate studies, which concerns examining the

climate in Earth's past, revealed that glaciers covered large areas of the world which also are now

separated by great geographic distances. These observations seemed to indicate that the Earth's

lithosphere had been moving over geologic time.

Wegener's ideas were very controversial because he didn't have an explanation for why the

continents moved, just that there was observational evidence that they had. At the time, many

geologists believed that the features of the Earth were the result of the Earth going through cycles of

heating and cooling, which causes expansion and contraction of the land masses. People who

believed this were called the anti-mobilists. The mobilists were in the opposite camp and supported

Wegener's ideas, since many of them had seen evidence for continental motion, especially in the

Alps.

Although Wegener's "continental drift" theory was later disproved, it was one of the first times that

the idea of crustal movement had been introduced to the scientific community; and it laid the

groundwork for the development of modern plate tectonics. As years passed, more and more

evidence was uncovered to support the idea that the plates move constantly over geologic time.

Paleomagnetic studies, which examine the Earth's past magnetic field, showed that the magnetic

north pole seemingly wandered all over the globe. This meant that either the plates were moving, or


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else the north pole was. Since the north pole is essentially fixed, except during periods of magnetic

reversals, this piece of evidence strongly supports the idea of plate tectonics.

Following World War II, even more evidence was uncovered which supports the theory of plate

tectonics. In the 1960's a world-wide array of seismometers were installed to monitor nuclear

testing, and these instruments revealed a startling geological phenomenon. It showed that

earthquakes, volcanoes, and other active geologic features for the most part aligned along distinct

belts around the world, and those belts defined the edges of tectonic plates.

In addition, further paleomagnetic studies revealed a striped pattern of magnetic reversals in the

crust of the ocean basins. Basalt contains a fair amount of magnetic minerals called magnetite.

When the lava from spreading centers in the oceans forms and cools, these minerals align to the

north pole. The Earth has undegone several magnetic reversals in the past, in which the north and

south poles are reversed for a period of time. When geologists and geophysicists discovered that thecrust in the ocean recorded these reversals, it was even more positive proof that the lithosphere had

to be in motion, otherwise there would be no "stripes" of normal and reversed polarity crust.

These were some of the final pieces of the puzzle that led to the development of modern plate

tectonic theory. Since its emergence in the 1960's, plate tectonic theory has gained wide-spread

acceptance as the model of Earth processes.

Continental Drift

Alfred Wegener first proposes Continental Drift in his book published in 1915. Suggests that 200

million years ago there existed one large supercontinent which he called Pangaea (All Land)

(Figure). This was not really a new idea, but Wegener offered several lines of evidence in support of

his proposal.

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.


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Fossil Similarities - Mesosaurus, (Figure) 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. (Figure)

Termination of mountain chains. (Figure)


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Paleoclimatic Evidence

Glacial deposits at equator

Coral reefs in Antarctica

Idea was rejected by North American geologists because Wegener couldn't come up with a

mechanism for continental drift. Suggested tidal forces, but physicists showed this to be impossible.

Wegener dies in 1930 and his idea dies with him.

Magnetism and Paleomagnetism

Earth is a bar magnet with a magnetic north and south. At poles a compass needle dips vertically.

Downward at the north pole, upward at the south pole and horizontal at the equator. Magnetic poles

do not correspond with geographic poles. Variation is termed the magnetic declination. It is 16degrees east in California. However, it has been found that even though the magnetic and

geographic poles do not correspond today when the location of the magnetic north pole is averaged

over a 5,000 year period it does correspond with geographic north. Magnetic pole moves as much as

25 km per year.

Causes of Earth's Magnetism

First thought to be the result of a permanently magnetized core. However, it has been shown that

when any substance is heated above 500 degrees C it looses its permanent magnetism.

Earth is a Dynamo - Outer core is a fluid consisting largely of iron, so it is an excellent conductor.

Electromagnetic currents are generated and amplified by motion within the liquid caused by


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convection. Rotation of the Earth unifies the random convective movements generating the

magnetic field.

Paleomagnetism

In the 1950's scientists discover how to measure paleomagnetism (magnetism frozen in the rock at

the time it formed). With this knowledge scientists could tell the direction and latitude of

geomagnetic pole at the time the rock formed. Europeans were the first to extensively study

paleomagnetic pole locations and found that by 500 MY ago magnetic north was located near

Hawaii. At first it was assumed the poles were free to wander (Apparent Polar Wandering). North

American geologists attempted similar studies largely to disprove the Europeans and found that 500

my ago North American rocks showed the magnetic north pole to be in the East Pacific, 3000 miles

to the west of the European magnetic north at that time.

At the same time a series of bathymetric surveys of the ocean basins revealed a system of ridges and

trenches with high heat flow over the ridges. H. Hess (1962) rushes to print with the idea of Sea

Floor Spreading. Postulates convection cells beneath ocean basins to drive the spreading.


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Fred Vines supports Hess with his explanation of symmetrical magnetic stripes on either side of the

Atlantic Mid-ocean ridge .

Plate Tectonics

Theory of Plate Tectonics is born. Plate - is a rigid piece of lithosphere floating on a partially plastic

substrate (asthenosphere).

Seven Major Plates

Pacific

North American

South American

African

Eurasian Antarctic


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Indo-Australian

Types of Plate Boundaries

Divergent - Spreading Center - Constructive Margin. Characterized by ocean ridges and sea floor

spreading.


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Convergent - Characterized by trenches and island arcs

Ocean - Ocean (Japanese

Islands)

Ocean - Continental (Cascade Mountains)

Continent - Continent (Himalayas)Transform - Plates moving past one another along strike- slip faults.

Additional Evidence in Support of Plate Tectonics

Distribution of earthquakes along plate margins

Location of earthquake foci along steeply-dipping subduction zones

Age dating sediments on either side of the ridge indicates the sediments get progressively older

away from the mid-ocean ridge axis

Thickness of sediments also increases away from ridge

Driving Force

Convection Cells

Hot Spots


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Name : Kharis Dani Azhari

Class : XII-IPA

Title : Diary of Anne Frank

Author : Anne Frank

Publisher : Penguin Books

10 Question

1. When and who is the diary given to Anne Frank?

2. When Anne's sister, Margot , is called to appear before the authorities, where is she being

sent?

3. Where is the Secret Annex ?4. When exactly is the first time she wrote the diary?

5. For how many years does the Frank Family lives in this Secret Annex?

6. What type of knowledge is Anne grows in Education?

7. When is the real change in Anne behaviour?

8. Who is she in love with? Peter Schiff or Peter Van Daan?

9. Why is Anne becomes harder on herself and berating herself to being mean to the other

members of the Annex?

10. When is the last time she wrote the diary after the secret annex is raided?

10 Vocabulary

1. Curfew : an order establishing a specific time in the evening after which certain

regulations apply, especially that no civilians or other specified group of unauthorized

persons may be outdoors or that places of public assembly must be closed.

2. ardor : great warmth of feeling; fervor; passion

3. evidently : obviously; apparently.

4. incurable : not curable; that cannot be cured, remedied, or corrected

5. dismally : causing gloom or dejection; gloomy; dreary; cheerless; melancholy

6. submission : an act or instance of submitting.

7. forbidden : to command (a person) not to do something, have something, etc., or not to

enter some place

8. deportation : being transfer

9. crammed : load something forcibly

10. oppressive : bully someone roughly

earth makalah

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