2. Composition of Earth
Earth Has 4 main systems that interact:
Earth’s
systems
Atmosphere
Hydrosphere
Biosphere
Geosphere
Air/gases
water
life
land/rock
4. Atmosphere.
How do you know its there
Is
this “air” that surrounds us considered
matter? Does it weigh anything? How do you
know?
Think about it and decide on an answer.
Talk in groups with the person who sits by
you
Be ready to tell the class what you decided
and why.
5. Weight of the atmosphere
Gases
are in the
atmosphere.
They are things we
learned about in the
periodic table:
Nitrogen, Oxygen,
Carbon Dioxide,
Hydrogen
It is matter! Sound
can travel through it.
6. Even though you can’t see
them, Atoms make up gases.
Are
some atoms bigger than others?
Are their atomic weights all the same?
7. Helium vs. Carbon Dioxide
Do you think of helium
as light and floating or
heavy and falling?
Do you think about
Carbon Dioxide as light
and floating or heavy
and falling….think about
the gas released from
dry ice… does it go up
or down?
http://jp.youtube.com/watch?v=F239
8.
Composition of Earth
Earth Has 4 main systems that interact:
The Atmosphere
Mostly Nitrogen and Oxygen
Water vapor is responsible for clouds and
precipitation
Has layers
Protects us from meteors and comets, x-rays,
gamma rays, ultra violet light
The Hydrosphere
The Biosphere
The Geosphere
9. Composition of Earth’s atmosphere
Earth Has 4 main systems
that interact:
The Atmosphere
Troposphere
The layer of the atmosphere
closest to the earth.
There are 5 layers of the
atmosphere seen to the right.
Exosphere
11. Troposphere and Clouds
Among other gases there is water vapor in
the troposphere.
Clouds—form when air rises, cools to its dew
point, and becomes saturated (moist).
15. Section 2: Earth’s Weather
Troposphere
Weather—the atmosphere’s condition in
terms of temperature, cloud cover, wind
speed and direction, humidity, and air
pressure.
What are different types of weather?
___________________________________
___________________________________
___________________________________
___________________________________
16. Section 2: Earth’s Weather
Troposphere
Temperature—a measure of how fast air
molecules are moving.
When molecules are moving rapidly,
temperature is high.
Celsius and Fahrenheit thermometers measure
air temperature.
17. Section 2: Earth’s Weather
Troposphere
What
is the temperature like today?
Hot/ Cold ______________________
Degrees Fahrenheit_______________
Degrees Celsius _________________
18. Section 2: Earth’s Weather
Troposphere
Energy is transferred between fast-moving
molecules and slower-moving molecules.
Give an example of something heating up due to
conduction:
__________________________________
Conduction—transfer of energy when molecules collide.
Convection occurs when warm air rises and cool air sinks.
Give an example of something heating up due to
convection:
___________________________________
19. Section 2: Earth’s Weather
Troposphere
Air pressure— air weight that varies over
Earth’s surface.
Warmer air is less dense and exerts less
pressure.
Cooler air is more dense and exerts more
pressure.
21.
Humidity— the amount of water vapor in
the air
Temperature affects how much moisture is
in the air.
22. Composition of Earth
Earth
The Atmosphere
The Hydrosphere
Has 4 main systems that interact:
All of Earth’s water, whether in the atmosphere,
glaciers, oceans, lakes or rivers.
The Biosphere
The Geosphere
23. Composition of Earth
Earth Has 4 main systems that interact:
Earth’s
systems
Atmosphere
Hydrosphere
Biosphere
Geosphere
Air/gases
water
life
land/rock
29. The Hydrosphere
Water on Earth is a unique feature that clearly
distinguishes our "Blue Planet" from others in
the solar system.
Not a drop of liquid water can be found
anywhere else in the solar system. Earth has
just the right mass, the right chemical
composition, the right atmosphere, and is the
right distance from the Sun that permits water
to exist mainly as a liquid.
Water is the universal solvent and the basis of
all life on our Planet.
30. Our Water Cycle
Water,
which covers the majority of the Earth’s
surface (the hydrosphere), circulates through the
crust, oceans, and atmosphere in what is known
as the water cycle.
31. Water Cycle—water is in constant
motion
The Sun provides water cycle’s energy
Water on the surface absorbs heat and
evaporates, entering the atmosphere
Condensation—water vapor changes back into
liquid.
Clouds of water become heavy and water falls to
Earth as precipitation.
The cycle repeats itself continuously.
32. The Water Cycle
http://www.kidzone.ws/water/index.html
Run and get a glass of water and put it on the table
next to you. Take a good long look at the water.
Now -- can you guess how old it is?
The water in your glass may have fallen from the sky
as rain just last week, but the water itself has been
around pretty much as long as the earth has!
When the first fish swam in the ocean, your glass of
water was part of that ocean. When the
Brontosaurus walked through lakes feeding on
plants, your glass of water was part of those lakes.
When kings and princesses, knights and squires
took a drink from their wells, your glass of water was
part of those wells.
And you thought your parents were OLD
33. Evaporation:
Evaporation
is when the sun heats up water
in rivers or lakes or the ocean and turns it into
vapor or steam. The water vapor or steam
leaves the river, lake or ocean and goes into
the air.
34. Do plants sweat?
Well, sort of.... people perspire
(sweat) and plants transpire.
Transpiration is the process
by which plants lose water
out of their leaves.
Transpiration gives
evaporation a bit of a hand in
getting the water vapor back
up into the air.
35. Condensation:
Water vapor in the air gets cold
and changes back into liquid,
forming clouds. This is called
condensation.
You can see the same sort of
thing at home... pour a glass of
cold water on a hot day and
watch what happens. Water
forms on the outside of the
glass. That water didn't
somehow leak through the
glass! It actually came from the
air. Water vapor in the warm
air, turns back into liquid when it
touches the cold glass.
36.
37. Precipitation:
Precipitation
occurs when so
much water has condensed
that the air cannot hold it
anymore. The clouds get
heavy and water falls back to
the earth in the form of rain,
hail, sleet or snow.
38. Collection:
When water falls back to earth
as precipitation, it may fall
back in the oceans, lakes or
rivers or it may end up on
land. When it ends up on
land, it will either soak into the
earth and become part of the
“ground water” that plants and
animals use to drink or it may
run over the soil and collect in
the oceans, lakes or rivers
where the cycle starts
39. Fill in the diagram in your notes
The earth has a limited
amount of water. That
water keeps going
around and around and
around and around and
(well, you get the idea)
in what we call the
"Water Cycle". This cycle
is made up of a few main
parts:
evaporation (and
transpiration)
condensation
precipitation
collection
40.
41.
42.
Accumulation - the process in which water pools in large bodies (like
oceans, seas and lakes).
Condensation - the process in which water vapor (a gas) in the air turns
into liquid water. Condensing water forms clouds in the sky. Water drops
that form on the outside of a glass of icy water are condensed water. (This
term appears twice in the diagram.)
Evaporation - the process in which liquid water becomes water vapor (a
gas). Water vaporizes from the surfaces of oceans and lakes, from the
surface of the land, and from melts in snow fields.
Precipitation - the process in which water (in the form of rain, snow, sleet,
or hail) falls from clouds in the sky.
Subsurface Runoff - rain, snow melt, or other water that flows in
underground streams, drains, or sewers.
Surface Runoff - rain, snow melt, or other water that flows in surface
streams, rivers, or canals.
Transpiration - the process in which some water within plants evaporates
into the atmosphere. Water is first absorbed by the plant's roots, then later
exits by evaporating through pores in the plant.
45. Bill Nye’s take on the water
cycle…
http://jp.youtube.com/watch?v=ZQIVx_BOCJU
http://jp.youtube.com/watch?feature=related&hl=en&v=2XU9_
http://jp.youtube.com/watch?v=dGSkcrw00HM&feature=relate
46. Composition of Earth
Earth Has 4 main systems that interact:
Earth’s
systems
Atmosphere
Hydrosphere
Biosphere
Geosphere
Air/gases
water
life
land/rock
47. Composition of Earth
Earth
The Atmosphere
The Hydrosphere
The Biosphere
Has 4 main systems that interact:
Life on Earth
Sea life, plants, flying creatures, humans
Encompasses hydrosphere, upper geosphere, and
lower atmosphere.
The Geosphere
50. Living things interact with Non
living things in the Biosphere
Biotic Factors—
living components
in the biosphere
Biotic, meaning of
or related to life, are
living factors.
Plants, animals,
fungi, protist and
bacteria are all
biotic or living
factors.
51. Living things interact with Non
living things in the Biosphere
Abiotic Factors—
nonliving
components in the
biosphere
Environmental
factors such habitat
(pond, lake, ocean,
desert, mountain) or
weather such as
temperature, cloud
cover, rain, snow,
hurricanes, etc. are
abiotic factors.
52. Role of Water in the Biosphere
Water
is the
universal solvent
and the basis of
all life on our
Planet.
The hydrosphere
is important to the
Biosphere!
53. Role of the Sun for the biosphere
The
Sun
provides the
light and heat
necessary to
maintain life
on Earth and
is the ultimate
source of
energy.
54. Biotic
and abiotic factors combine to create a
system or more precisely, an ecosystem.
An ecosystem is a community of living and
nonliving things.
58. The Impact of Changing Factors
If
a single factor is changed, perhaps by
pollution or natural phenomenon, the whole
system could be altered.
For example, humans can alter environments
through farming or irrigating. While we
usually cannot see what we are doing to
various ecosystems, the impact is being felt
all over.
For example, acid rain in certain regions has
resulted in the decline of fish population.
59. A food chain
Shows how each living thing gets its food.
Some animals eat plants and some animals eat other
animals.
For example, a simple food chain links the trees, the
giraffes and the lions. Each link in this chain is food for
the next link. A food chain always starts with plant life
and ends with an animal.
60. A food chain
An is added and means “is eaten by”; also shows
the flow of energy (the giraffe gets his energy from the
leaves)
Now we have made a simple food chain.
65. Animals
cannot make their own food so they
must eat plants and/or other animals. They
are called consumers or heterotrophs.
There are three groups of consumers.
66. Herbivores
are animals that only eat plants
or plant products (seeds). They are also
called primary consumers
68. Secondary
Consumers
are carnivores that eat
herbivores
Herbivores are primary
consumers
Something that makes its
own food is called a
producer
69. Tertiary consumers are
carnivores that eat
other carnivores
killer whales (tertiary
consumer—they eat
another carnivore)
Dolphin (secondary
consumer—they eat a
herbivore)
Herring (primary
consumer—they only eat
plants)
Photoplankton (this
plant produces its own
food)
70. Make your own food chain
Find
in your notes where it says to make your
own food chain.
Start with a plant on the very left side.
The arrow means “is eaten by” so think of the
next thing that might eat your plant…and so
on.
71. Animals
and people who eat BOTH animals
and plants are called omnivores
WE EAT PLANTS
WE EAT MEAT
72. To sum up:
Animals that eat
only plants.
Animals that eat
only animals.
Animals that eat
both animals AND plants
. Humans are also
omnivores!
73. Then there are decomposers (bacteria, worms,
and fungi) which feed on decaying matter.
These decomposers speed up the decaying
process that releases mineral salts back into the
food chain for absorption by plants as nutrients.
78. In a food chain, energy is
passed from one link to another
Lets say a plant has the # 100 to represent the
energy it has made.
When a herbivore eats, it does not get all the
plant’s energy. It uses up some of the energy in
everyday activities. The herbivore may only get
10% of that energy.
A carnivore then eats this herbivore. The
carnivore only gets 1% of that plants original
energy. This is why the carnivore has to eat many
herbivores to get enough energy to grow.
79. Energy
and mass is transferred from
one level of the food chain to the next
with an efficiency of about 10%.
80. ENERGY’S MOVEMENT IN THE FOOD CHAIN
Because of the
large amount of
energy that is lost at
each link, the
amount of energy
that is transferred
gets lesser and
lesser
The further along
the food chain you
go, the less food
(and energy)
remains available.
81.
82. This energy pyramid shows many
trees & shrubs providing food and
energy to giraffes.
Note that as we go up, there are
fewer giraffes than trees & shrubs
and even fewer lions than giraffes
... as we go further along a food
chain, there are fewer and fewer
consumers.
In other words, a large mass of
living things at the base is required
to support a few at the top ... many
herbivores are needed to support a
few carnivores
83.
84.
85. Most
food chains have no more than four or
five links
There cannot be too many links in a single
food chain because the animals at the end of
the chain would not get enough food (and
hence energy) to stay alive.
86. Most
animals are part of more than one food
chain and eat more than one kind of food in
order to meet their food and energy
requirements. These interconnected food
chains form a food web.
88. Note
that the arrows are drawn from food
source to food consumers ...
substitute the arrows with the words "eaten
by"
The arrows also show the way energy is
moving.
89.
90. Recap
The sun is the source of energy
Water is the source of life on earth
Water is in the hydrosphere, geosphere and
atmosphere, and biosphere.
The living things in the biosphere are dependent on
many nonliving things. (abiotic and biotic)
There are food chains and webs that show what
animals eat. The higher up on the food chain, the
less predators they have.
Be able to describe who receives the most of the
sun’s energy and how energy moves and is
converted through the food chain.
Be able to describe how the systems are connected
(atmosphere, hydrosphere, and biosphere)
93. Composition of Earth
Earth Has 4 main systems that interact:
Earth’s
systems
Atmosphere
Hydrosphere
Biosphere
Geosphere
Air/gases
water
life
land/rock
94. Composition of Earth
Earth
Has 4 main systems that interact:
The Atmosphere
The Hydrosphere
The Biosphere
The Geosphere
The solid earth (rock)
Continental earth, and solid earth (continental crust)
under water and the oceans (oceanic crust)
97. Name four properties (or
clues) that scientists use
to identify minerals.
Color, luster, streak,
and hardness
98. Property of mineral: color
The
color of a rock can be a clue to what it
is made up of. Sometimes the color can help
you figure out what it is, other times it can
fool you.
Copper is reddish
Sulfer is yellowish
99. Sometimes the color can help you
figure out what it is, other times it can
fool you.
WHICH
ONE IS GOLD? WHICH ONE IS PYRITE,
OR BETTER KNOWN AS FOOLS GOLD.
100. Did you guess?
As you can see…
Color
may be misleading.
GOLD
FOOLS GOLD
106. Property of mineral: hardness
How
tightly the atoms are bonded together in
the rock…. How HARD or soft is the mineral?
107. What are three testers
that can be used to
determine a mineral’s
hardness?
fingernail, penny, nail
108. TYPES OF ROCKS
Classified by how they
Are formed.
IGNEOUS ROCKS
SEDIMENTARY
METAMORPHIC
(melted rock from inside
The Earth cools)
(sediment collects in
Layers that form rocks)
(rocks form from
Pressure and temp)
EXTRUSIVE
Melted rock cools
Melted rock that reaches
The surface is called lava.
INTRUSIVE
Magma forced up but
Doesn’t reach surface
Magma—melted rock that
Doesn’t reach the earth.
112. Origin of Igneous
Classified according to where they are
found.
Extrusive
rock— formed from lava that
erupted onto the Earth’s surface. Fine
grained. (ex. Basalt)
Intrusive
rock— formed when magma
hardens beneath the Earth’s surface.
Coarse grained. (ex. Granite)
113. EXTRUSIVE ROCKS (lava)
Extrusive
Rocks Form 2 ways
Volcanoes erupt and shoot out lava and ash.
Large cracks in Earth’s crust (fissures), can open
up. Lava oozes out onto ground or into water.
115. Sediments form Rock
Form
from particles deposited by water
and wind.
Sediment—small,
solid pieces of
material that come from rocks or living
things.
Water,
wind, and ice can carry
sediment and deposit it in layers.
116. Examples of Sediment
Mud
Pebbles
Shells
Bones
Sand grains
Leaves stems
Living remains
Over time, any remains from living may slowly harden
and change into fossils trapped in the rock.
117. Sedimentary rocks form in 3
ways:
Detrital
Rocks
Made up of grains of
minerals or other rocks.
The weight of the sediments
squeezes them into layers.
118. Sedimentary rocks form in 3
ways:
Organic
rocks— formed from fossils (the hard
parts of dead organisms like bones/ shells
119. Sedimentary rocks form in 3
ways:
Chemical
Rocks
Seawater filled with
minerals
evaporates. As
water evaporates,
layers of minerals
are left behind.
120. Types of Sedimentary Rock
Clastic (Detrital Rocks)
Forms when rock fragments are squeezed
together. (ex. Sandstone)
Organic Rocks
Forms where remains from plants/ animals
are deposited. (ex. Coal and limestone)
Chemical Rocks
Forms when minerals that are dissolved in a
solution crystallize.
124. Erosion
Destructive
forces break up and wear away
present rock.
Heat, cold, rain, waves, grinding ice
Running water or wind loosen and carry away
the fragments of rock.
125. Deposition
The
process by which sediment settles out of
the water or wind carrying it.
The eroding water or wind slows and
deposits the sediment.
If carried by water, rock fragments and other
materials sink to the bottom of a lake or ocean.
http://www.classzone.com/books/ea
rth_science/terc/content/visualizatio
ns/es0604/es0604page01.cfm?
chapter_no=visualization
126. Compaction
Its been moved away and now dropped.
Heavy thick layers of sediment build up
The weight presses down on the layers
Compaction—process that presses
sediments together.
Each year, new sediments fall creating new
layers.
The layers are often visible
127. Cementation
The
process in which dissolved minerals
crystallize and glue particles of sediment
together.
Where loose sediments become solid
sedimentary rock
Minerals dissolve in water and then seep into
spaces between sediment.
128. Review:
Processes that change sediment
into sedimentary rock
1.
2.
3.
4.
Erosion
Deposition
Compaction
Cementation
http://www.classzon
e.com/books/earth_
science/terc/content/
investigations/es060
2/flash/es0602_p02
_rockcycle.swf
130. Metamorphic Rocks
Heat
and pressure deep in the Earth can
change any rock into a metamorphic rock.
Heat from mantle
Pressure due to depth. Minerals can change into
other minerals.
131. Classifying Metamorphic Rocks
Arranged by the grains that make up the rocks.
Foliated—grains arranged in parallel layers/ bands
(slate, schist, gneiss)
Nonfoliated—Mineral grains are arranged
randomly (marble and quartzite)
133. Rock Cycle
A
series of processes on Earth’s surface and
inside the planet that slowly change rocks
from one kind into another.
Earths constructive and destructive forces
(and plate tectonics) move rocks through the
rock cycle.
Quiz: http://www.learner.org/interactives/rockcycle/diagram2.html
http://www.learner.org/interactives/rockcycle/diagram.html
http://www.cdli.ca/CITE/rocks_general.htm
134.
135. Memorize this!!!
Rock Cycle Song
(Sing to the tune of "Row, Row, Row Your Boat")
SEDIMENTARY rock
Has been formed in layers
Often found near water sources
With fossils from decayers
Then there's IGNEOUS rock
Here since Earth was born
Molten Lava, cooled and hardened
That's how it is formed
These two types of rocks
Can also be transformed
With pressure, heat and chemicals
METAMORPHIC they'll become.
137. REVIEW POINT
Major Concepts
Identify
and describe the 4 major systems that
interact on Earth.
Explain how water might be involved in all 4
systems.
Explain how the Sun is important to life on
Earth
140. The Geosphere – solid Earth
The
geosphere is in a constant state of
motion that gives rise to movement of the
continents.
The
unifying theory that explains how
continental drift is possible is called plate
tectonics, which was developed by geologists
in the 1960s.
141. Earth has 4 layers
Earth has four layers
Outermost layer is the crust.
Solid layer that flows slowly like putty is the
mantle.
Outer core— molten metal above the inner core.
Inner core— dense iron core; very hot and dense.
142. Why/ How is the geosphere in
constant motion?
143. Plate boundaries are edges where
plates meet.
Tension can pull plates apart, resulting in new
lithosphere forming in the gaps.
Colliding plates could cause mountains to form
as rock crumbles and folds.
Subduction occurs when a denser plate sinks
underneath a less dense plate.
Shearing causes faults and earthquakes as two
plates slide past each other.
144. Plate movement theory—
convection in the mantle circulates
material and moves plates.
Ridge-push at mid-ocean ridges causes plates to
slide down the slope.
Slab-pull happens as plates move away from midocean ridges and become denser.
148. The Science of Geology
Geologists – scientists
who study the forces that
make and shape planet
Earth
Landforms – features
formed in rock and soil by
water, wind and waves
149. Geology – the study of planet
Earth
Studying surface changes
1. Constructive forces – shape the
surface by building up mountains
and landmasses.
Ex: land is made
Destructive forces – slowly wear
away mountains and other land
features.
Ex: land is destroyed
150. A Journey to the Center of the
Earth –
Temperature – at a depth of about 20m
the temperature gets warmer as you
go deeper into the earth’s interior. For
every 40 m, the temperature rises
1degree C, then it eventually increases
more slowly.
Pressure – the deeper you go the
greater the pressure (force pushing on
a surface of area)
151. The Crust – layer of rock that forms the Earth’s
outer skin. Includes soil, water, mountains, etc.
It is the thinnest layer – thinner beneath the
oceans than beneath the continents (5 – 40 km
thick)
Oceanic Crust – the crust beneath the oceans.
Consists mostly of basalt rock.
Continental crust – the crust beneath the
continents. Consists mostly of granite rock.
152. Second layer, nearly
3000 km thick. Top part
made of rigid rock similar
to the crust, lower part
made of softer rocks.
Lithosphere – the
crust and the upper
rigid part of the
mantle
Asthenosphere –
lower part of the
mantle made of soft
rocks that can flow
like a liquid (have
plasticity)
153. The Core
Consists of two parts
Outer core – made of
molten metal. (2250
km thick)
Inner core – a dense
ball of solid rock.
(1200 km thick). The
pressure is so great
that the iron and nickel
cannot spread out and
become liquid.
155. Methods of Heat Transfer
Radiation
transfer of thermal energy (heat)
in the form of waves. Does not
require a medium. Ex: feeling
warmth from a fire.
156. Methods of Heat Transfer
Conduction –
heat transfer by
direct contact.
Ex: Handle of a
spoon in hot soup
also becomes
heated.
157. Methods of Heat Transfer
Convection – heat transfer
by currents moving through
a heated fluid (liquid or
gas).
Ex: Warm air rises and
cool air sinks in a room.
http://www.solarviews.com/eng/edu/convect.htm
158. Convection in the Earth’s Mantle
The (lower mantle) is heated by the outer core,
the heated rocks become less dense and rise,
while the cooler rocks from above sink. The
repeated process results in continuous cycles of
material.
160. Continental Drift
– theory that the continents had once been
joined together in a single landmass and
have since drifted apart.
Theory first proposed by Alfred Wegener
Pangaea – the one supercontinent believed to
have existed 300 million years ago
161. Evidence for Continental Drift
Alfred Wegener (18801930), a German
meteorologist and geologist,
was the first person to
propose the theory of
continental drift.
200 mya the continents
were originally joined
together, forming Pangaea,
meaning "All-earth".
162. Evidence for Continental Drift
Evidence from landforms
Mountain range – in Africa
matched a mountain range in
South America
European coal fields match
coal fields in North America
163. Evidence for Continental Drift
Evidence from Fossils
Fossil – trace of an organism
that has been preserved in rock
Mesosaurus – reptile whose
fossils were found in S. America
and Africa. This organism could
not have swum long distances
in salt water,
164. Evidence for Continental Drift
Evidence from fossils (continued)
Lystrosaurus
– reptile whose fossils were
found in Africa and India. This organism
could not have swum across the ocean.
Glossopteris – a seed fern plant. Identical
fossils were found in S. America, Africa,
Antarctica, India and Australia. /seeds
could not have traveled by air or water
across vast oceans.
165. Evidence for Continental Drift
Evidence from climate
Spitsbergen island – located in
the Arctic Ocean, north of
Norway. Fossils of tropical
plants have been found there.
Evidence that continental
glaciers once covered S. Africa
166.
167. Scientists Reject
Hypothesis
Wegener could not provide a satisfactory
explanation for the force that pushes or
pulls continents
geologists rejected the theory
(until new evidence was discovered later.)
169. Mid-ocean ridge – longest chain
of mountains in the world
Where volcanic and
earthquake activities occur
Rift Valley – runs lengthwise
through
the mid-ocean ridge
170. The Theory of Sea-Floor Spreading
Harry Hess in 1960
The ocean floors move like conveyer
belts, carrying the continents with them.
Since the continents are attached to the
ocean floor, sea-floor spreading could
be the force causing the continents to
move.
171. The theory of sea floor spreading
At mid-ocean ridges molten
material rises from the
mantle and erupts.
The molten material then
spreads out, pushing older
rock to both sides of the
ridge.
172.
Evidence from Molten Material –
scientists discovered “pillow
lava” forming along the midocean ridge. These rocks form
when molten material hardens
quickly after erupting under
water.
Evidence from Magnetic Stripes –
patterns of magnetic stripes
match on either side of the midocean ridge, suggesting that the
ocean floor is spreading evenly in
opposite directions.
173. Evidence (continued)
Evidence From Drilling Samples – The
Glomar Challenger, a drilling ship, drilled
holes in the ocean floor. Discovered that
rocks along
mid-ocean ridges are
much younger
than rocks farther away.
174. Subduction at Deep—
Ocean Trenches
Subduction – process whereby the ocean floor
plunges into the mantle and melts at deep
underwater canyons called deep-ocean
trenches.
175. Subduction at Deep—
Ocean Trenches
Subduction and Sea-Floor Spreading work
together like a conveyor belt, moving the
continents.
176. Subduction at Deep—
Ocean Trenches (cont.)
Subduction and the Earth’s Oceans
Subduction in the Pacific Ocean – the deep
trenches surrounding the Pacific Ocean result in
more subduction that sea-floor spreading. The
result is that the Pacific Ocean floor is getting
smaller.
Subduction in the Atlantic Ocean – the Atlantic
Ocean floor is becoming
177. TYPES OF PLATE MOVEMENT
Divergence, Convergence, and Transform
At the boundaries of the plates, various
deformations occur as the plates interact;
they separate from one another (seafloor
spreading),
collide (forming mountain ranges),
slip past one another (subduction zones, in which
plates undergo destruction and remelting), and slip
laterally.
178. Divergent Plate Movement
Seafloor spreading is the
movement of two oceanic
plates away from each
other,
results in the formation of
new oceanic crust (from
magma that comes from
within the Earth's mantle)
Happens along a a midocean ridge.
Where the oceanic plates
are moving away from
each other is called a
zone of divergence.
179. Convergent Plate Movement:
When two plates collide, some
crust is destroyed in the impact
and the plates become smaller.
The results differ, depending upon
what types of plates are involved.
Oceanic Plate and Continental
Plate - When a thin, dense
oceanic plate collides with a
relatively light, thick continental
plate, the oceanic plate is forced
under the continental plate; this
phenomenon is called subduction.
Two Oceanic Plates - When two
oceanic plates collide, one may be
pushed under the other and
magma from the mantle rises,
forming volcanoes in the vicinity.
Two Continental Plates - When
two continental plates collide,
mountain ranges are created as
the colliding crust is compressed
and pushed upwards.
180. Lateral Slipping Plate Movement
When two plates move
sideways against each
other, there is a
tremendous amount of
friction which makes the
movement jerky.
The plates slip, then stick
as the friction and pressure
build up to incredible levels.
When the pressure is
released suddenly, and the
plates suddenly jerk apart,
this is an earthquake.