Download Oceanic Crust

The Sun is the driving force behind
weather, climate, and convection
–Weather changes from day to day.
–Climate = a region’s general pattern of
weather over a long period of time.
• The equator receives the most direct
angle of sunlight, creating the warmest
climates.
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Heating differences
causes there to be
different air masses.
cool air (or water) is
more dense than warm,
so it sinks, creating
currents by convection
sun heats land
and oceans by
radiation
land/ocean
heats the air
above it by
conduction
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Land-Ocean Interactions
Land heats up faster than water (= the ocean).
– The air over the land will also heat quickly.
– Warm air rises, starting a convection current.
– This brings moist ocean air inland.
• Ocean air holds a lot of water vapor.
• Warm air can also hold more water vapor.
– When air cools, it may no longer be able to
hold on to all of the water vapor, forming clouds
& precipitation.
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Air movements create weather changes.
Air mass = A body of air that has similar pressure,
temperature, & humidity.
•Different air mass pressures cause wind.
• Air moves from high to low pressure areas.
-Generally blow from poles toward equator
-Weather often changes when air pressure changes
-A front is where two air masses meet or collide
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Frontal Systems Symbols
Weather Map
• Oceans can also influence weather in
extreme ways, such as in the formation of
hurricanes.
= A low pressure tropical storm that forms over ocean
water.
• Oceans impact climate because they heat
and cool slowly (=good insulator!).
– Land near the ocean is often warmer in winter and
cooler in summer, meaning inland climates differ
from those near the ocean at the same latitude.
• Oceans also impact climate via currents…
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Current – movement of water in the ocean
• Surface currents are affected by  Winds
 Continental deflections
 Coriolis Effect – following the
curve of the Earth as it rotates
• Deep ocean currents are affected by  Temperature differences (density)
 Salinity differences (density)
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Movement of currents is constant and
creates a “global conveyor belt” that
transfers heat from one part of the
Earth to another via water.
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Plate Tectonics and Continental Drift
Alfred Wegener
1912 - proposed that all the continents were
once joined as a single landmass
– he called this “supercontinent” Pangaea
– stated the continents have separated and
collided as they have moved over millions of
years
– called his theory “continental drift”
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Plate Tectonics
• The Earth’s crust is divided into 12 major plates
which are moved in various directions.
• This plate motion causes them to collide, pull
apart, or scrape against each other.
• Each type of interaction causes a characteristic set
of Earth structures or “tectonic” features.
• The word, tectonic, refers to the deformation of
the crust as a consequence of plate interaction.
Wegener’s 5 major pieces of Evidence:
1. Continents (esp. South America & Africa)
seem to fit together like pieces of a
puzzle
2. Matching fossils occur on east coast
of S. America & west coast of Africa
3. Matching folded mountain belts on
coasts of S. America & Africa
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Evidence cont…
4. Evidence of ancient climates
show landmasses were once
located elsewhere
- Ex: glaciers in Africa !
5. Data for latitudes &
longitudes of locations is
changing
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The Earth’s Layers cont…
•
Crust
– outermost layer
– thinnest layer
– the layer we live on
– divided into pieces, called tectonic plates
– two types: continental and oceanic crust
• Mantle
– thickest layer
– “flows” and allows the tectonic plates to move on top
– primarily magma
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The Crust
• This is where we live!
• The Earth’s crust is made of:
Continental Crust
Oceanic Crust
- thick (10-70km)
- buoyant (less dense
than oceanic crust)
- mostly old
- thin (~7 km)
- dense (sinks under
continental crust)
- young
Plate Movement
• “Plates” of lithosphere are moved around by the
underlying hot mantle convection cells
Three Types of Plate Boundaries
• Divergent
• Convergent
• Transform
http://www.learner.org/interactives/dynamicearth/plate.html
Divergent Boundaries
• Spreading ridges
– As plates move apart new material is erupted to fill
the gap
Convergent Boundaries
• There are three styles of convergent plate
boundaries
– Continent-continent collision
– Continent-oceanic crust collision
– Ocean-ocean collision
Continent-Oceanic Crust Collision
• Called SUBDUCTION example..Andes Mountains
Continent-Continent Collision
• Forms mountains, e.g. European Alps, Himalayas
Ocean-Ocean Plate Collision
• Island arcs and deep oceanic trenches..Japan
Mariana Trench
Plate Tectonics Summary
• The Earth is made up of 3 main layers (core,
mantle, crust)
• On the surface of the Earth are tectonic plates
that slowly move around the globe
• Plates are made of crust and upper mantle
(lithosphere)
• There are 2 types of plates
• There are 3 types of plate boundaries
• Volcanoes and Earthquakes are closely linked to
the margins of the tectonic plates
TOPO MAPS
• A topographic map is a two
dimensional representation of
three dimensional space.
• Utilizes contour lines to show
elevation.
• Contour lines are lines of equal
elevation.
• Elevation is distance above sea level.
• A contour line connects points of the same
elevation
• If you walked around an entire mountain
staying on the same contour line, you
wouldn’t change elevation.
Index contours
• If we wrote the elevation of every
contour line on that line, then our
map would be covered in numbers.
• Instead, we use index contour lines.
1. Usually darker lines
2. Have the elevation marked on them
Index contours
Rules for Contour Lines
• Contour lines always close to
form an irregular circle, it’s
just that sometimes you can’t
see the complete thing.
• Contour lines will make a ‘v’ in
the upstream direction a of a
stream.
Rules for Contour Lines
What is the contour
interval
This entire line represents
1200 feet above sea
level.
Rules for Contour Lines
Contour lines NEVER,
EVER cross
What’s going on?? Is this
area above or below
1200 feet?
?
What does contour line spacing indicate?
The closer together the
contour lines are, the
steeper the hill is. The
more spread apart they
are, the gentler the
slope.
Traveling along the red
line would be much
steeper than traveling
along the green line.
Weathering and Erosion
Topo maps show changes over time to the
Earth’s surface caused by weathering and
erosion
Weathering is the breakdown and alteration of
rocks and minerals at or near the Earth's
surface
Erosion
• Erosion is the
wearing away
of land or soil
by the action
of wind, water,
or ice.
http://www.ars.usda.gov/is/graphics/photos/k5951-1.htm