Download Earth, Yesterday, Today and Tomorrow

6th grade science
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Geologists plot earthquakes on maps to
analyze patterns in the data.
www.earthquakes.usgs.gov/earthquakes.
An Earthquake is the shaking or trembling of
the Earth due to the movement of tectonic
plates.
Magnitude is the amount of energy released
by an earthquake; magnitude relates to the
Strength of an Earthquake.
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About 20 earthquakes each day are recorded.
(Nothing less than a 2 is recorded).
About 9,000 very minor (below a 3)
earthquakes occur daily.
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Yearly about:
130,000 earthquakes between a 3- 3.9
13,000 earthquakes between a 4- 4.9
1,300 earthquakes between a 5-5.9
130 earthquakes between a 6 -6.9
17 earthquakes between a 7- 7.9
1 earthquakes between a 8 +
This is Amazing stuff!!
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Suggest all continents were once connected
( Pangea)
Evidence- The continents fit like a puzzle and
the same fossils have been found on
continents separated by an ocean.
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Describes the motion of Earth’s plates.
Tectonic plates are thick moving slabs of
rock. They include the crust and upper most
solid part of the mantle (called the
lithosphere).
The plates are in constant motion due to hot
convection currents produced by the molten
rock(magma) in the mantle.
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The plates move only a few centimeters each
year.
The plates can move into one another, away
from one another, or across one another.
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The plates can move into one another, away
from one another, or across one another.
The interaction of plates changes Earth’s
surface through earthquakes, volcanoes,
tsunamis, trenches, and mountains.
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It is at plate boundaries where most
earthquakes and volcanoes occur.
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Divergent
When 2 continental plates move apart a deep
valley rift forms( new crust results).
Look at page 45
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Sea Floor Spreading
When 2 ocean plates spread apart, a midocean ridge forms(new crust). Molten material
rises from convecting mantle and erupts.
The molten material hardens and pushing
older rock to the side. (page 45).
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Convergent-Oceanic/Continental
When an ocean plate and Continental plate
collide, the ocean plates will slide under the
harder, less dense continental plate.
Mountains result( possibly volcanoes).
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Convergent-Continental/Continental
The collison of 2 continental plates results in
the formation of Mountains.
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When 2 ocean plates collide, one slide under
the other and part of the rock melts. The
molten rock rises through the cracks/ holes
forming volcanic eruptions.
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Transform
When 2 continental plates against each other,
the rubbing and friction create great
pressure. An earthquakes results! ( pg.44)
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Earthquakes, mountains, and volcanoes most
often occur at the boundaries or Earth’s
tectonic plates.
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Most of the plates that are moving apart are
found at the bottom of the ocean. New
oceanic crust forms as magma rises to the
ocean floor. The longest mountain range in
the world, the Mid-Atlantic Ridge, was
formed this way.
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When two continental plates bump into each
other, they fold up. The Himalayan Mountains
were formed when India slammed into the
Asian plate about 50 million years ago.
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When a land plate (granite) collides with an
ocean plate(basalt), the oceanic crust slides
under the land(basalt is less dense than
granite). As it sinks some of it melts into
molten rock. The molten rock comes up
through the crust creating a volcano.
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When 2 oceanic crusts collide, one plate
slides under the other causing the formation
of a trench(deepest part of the ocean) as well
as underwater volcanoes. Underwater
volcanoes may some day rise above the water
and become islands.
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Plates can rub against each other along a
fault line. Sometime they stick as they grind
past one another. Great stress and pressure
builds up; when it becomes too great, the
rocks move causing great vibrations,
Earthquakes.
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The three types of plate boundaries and
movement.
Convergent boundaries- 2 plates moving
together and forming mountains or
volcanoes.
Divergent boundaries- 2 plates spreading
apart, forming rift valleys or mid-ocean
ridges- new crust is formed.
Transform Boundaries- 2 plates that slide
past each other releasing energy in the form
of earthquakes (caused by pressure).
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A magnet is a material that has the ability to
attract iron, steel, nickel, and cobalt.
Metals that are attracted to a magnet have
the ability to become magnetized themselves(
their atoms can be aligned).
The atoms in a magnet are aligned.
A magnet can make another object a
temporary magnet. Rub the object repeatedly
in the same direction with a magnet and the
atoms will become organized (aligned).
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The poles are the strongest part of a magnet.
Each magnet has a north and a south pole.
Opposites attract! Like Poles repel!
North >South Attract
South/South or North/North repel (push or
pull).
The magnetic field is the magnetized area
surrounding a magnet.
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The Earth is a giant magnet. It is very similar
to a bar magnet.
Scientists believe that Erath’s magnetic field
is due to electrical currents produced by
convection and rotation of the liquid outer
core and inner most layer of mantle.
The motion of the liquid creates an electrical
current that causes Earth to behave like a
magnet.
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The Earth has a magnetic north and south
pole. The Earth’s magnetic field attracts
materials that are magnetized.
The needle of a compass is a magnet so it
has a north and south pole.
The colored end of the compass needle is
“north seeking” so it is attracted to Earth’s
“magnetic north”( which is slightly different
from Earth’s geographic North pole.)
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When travelers can tell which way is north (by
the needle on the compass pointing north)
they can easily identify south, east, and west.
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Fossil evidence leads scientists to believe that
the continents were one large land mass
(Pangea) hundreds of millions of years ago.
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Sedimentary rocks are formed when
sediments and plants and animal remains pile
up and under great pressure , cement
together.
The oldest rock layers are on the bottom and
the newest are on top.
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Over millions of years as Earth changed, the
swamps, lakes, and seas became land
masses. Scientists have been able to find
fossils within sedimentary rock to learn
Earth’s history.
Some of the fossils from the continent to
continent were of the same species of plant
and animal. This provides support for the
theory of continental drift.
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Formed in several different ways:
Most fossils form when a plant or animal dies
and is buried by sediment which hardens over
the years into rock.
A mold or cast forms when the hard parts of
the organism are buried in the sediment.
Petrified fossils , such as wood, are fossils in
which minerals replace all or part of an
organism.
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Trace Fossils provide evidence of the
activities of ancient organisms. Foot prints
provide clues of an animals size (dinosaurs!)
and behaviors/activities.
Preserved fossil remains have little or no
change due to being preserved in sap, tar, or
ice.
Carbon film- a thin coating of carbon is left
behind on rock preserving the delicate parts
of leaves and insects.
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Geologists can learn:
The age of the fossils
Evidence of the types of plants/animals that
were once in an area.
Changes in climate and other environmental
conditions of an area( such as the presence of
ocean organisms lead us to the conclusion
that some land areas were once an ocean)
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The Earth has a very long history (4.6 billion
years). Scientists learn about major events in
the history of the earth by using rocks, rock
layers, and fossils.
The fossils in some layers of rock can be used
to determine the relative age of different rock
layers(its age compared to other rocks).
Law of superposition: in undisturbed rock,
the oldest layers are the lowest layers(oldest).
The youngest are on top.
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A gap in the geological record, usually caused
by erosion of old rock layers and the
deposition of new rock layers.
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All matter is made of atoms; if the atoms are
the same, the matter is an element( elements
include: carbon, oxygen, iron, lead and
potassium.
The rate of decay is an element's half- life.
The half-live is the time it takes for half of
the radioactive atoms to decay.
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Geologists use the geologic time scale to
show Earth’s History.
Geological time begins with the Precambrian
Period(88% of history) or the earth is 4.6
billion so 544 million years ago.
Between the Precambrian Period and now,
there are 3 long eras(ages): Paleozoic,
Mesozoic, and Cenozoic.