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PLATE TECTONICS
Inside Earth
Geologists are scientists who study the forces that make and shape the Earth.
Geologists study constructive and destructive force.
Geology is the study of the planet Earth.
Constructive forces shape the surface by
building up mountains and landmasses.
Destructive forces slowly
wear away mountains or
other features.
Journey to the Center of the EarthIf you were to take a journey
into the center of the Earth…the closer you get to the inside the HOTTER you would get!
Also, the deeper you go into the earth the more pressure you would feel.
As you travel to the center of the Earth you would pass through several different layers.
The 3 MAIN layers are:1. Crust2. Mantle3. Core
Earth’s Interior
Lithosphere and Asthenosphere
• Lithosphere- all of the crust and upper part of mantle
• Asthenosphere- the rest of the “flowable/liquidy” part of the mantle
THE CORE!!!
• There are currents (because of temperature and pressure) that cause the outer core to move, because it is more fluid than the SOLID inner core, they move at different rates.
• This provides our Earth with a MAGNETIC FIELD! Our planet works like a bar magnet which is why compasses point NORTH
Evidence for the Theory of Plate Tectonics
• Pangea
• Fossils
• Seafloor Spreading
• Let’s talk about each!
Drifting Continents
Alfred Wegener came up with a
hypothesis about the continents moving…..He
stated all continents were
once joined together in one
landmass “Pangaea” and since that time
they have drifted apart.
Continental Drift was Wegner’s idea that the continents slowly moved
over Earth’s surface
EVIDENCE: 1. landforms
2. fossils3. climate
Unfortunately, Wegener could not prove his theory…so scientist did not
believe him.
Fossil Evidence Map
What do you think the words “Sea Floor Spreading” mean?
How do you think this “sea floor” could spread?
Mid-Ocean Ridge: the under sea mountain chain where new ocean
floor is produced
At the mid ocean ridge, molten material rises from the mantle and erupts. The molten material then
spreads out, pushing older rock to both sides of the ridge.
Sea Floor Spreading: the process
by which molten
material adds new oceanic
crust to the ocean floor
EVIDENCE:1.Molten material
2.Magnetic strips
3.Drilling samples
Subduction at Deep Ocean Trenches
• Deep Ocean Trenches: a deep valley along the ocean floor through which oceanic crust slowly sinks towards the mantle
• Subduction: the process by which oceanic crust sinks beneath a deep-ocean trench back into the mantle
At deep-ocean trenches, subduction allows part of the ocean floor to sink
back into the mantle, over tens of millions of years.
Plate Tectonics
• Plate Tectonics is the theory that pieces of Earth’s lithosphere are in constant motion, driven by convection currents in the mantle
• The theory of plate tectonics explains the formation, movement, and subduction of Earth’s plates.
Convection Current?
• Convection currents is what cause the plates to move. Rocks closer to the center get hot and rise, rocks further away get colder and sink- a cycle/ current is created.
• There is also RADIATION- like heat from the Sun and CONDUCTION- heat by contact= other ways heat tranfers
Plate Boundaries
• Faults: a break in Earth’s crust where slabs of rock slip past each other
• Faults form along plate boundaries
• There are 3 types of Plate Boundaries
• Transform
• Divergent
• Convergent
Transform Boundaries
• A plate boundary where two plates move past each other in opposite directions
Divergent Boundaries
• A plate boundary where two plates move away from each other
• A deep valley called a rift valley can form along a divergent boundary
Convergent Boundaries
• A plate boundary where two plates move toward each other
• The collide or crash
Earthquakes
• Is the movement of rock beneath earth’s surface which causes the Earth to shake
STRESSED OUT!!! (force that changes shape or volume)
- Shearing- pulls rock in opposite directions, sliding
- Tension- Stretches rock apart, thins in middle
- Compression- squeezes rock together until folds or breaks
It’s all your FAULT!!!
• Occurs along plate boundaries
• Strike-slip- SHEARING force, TRANSFORM boundary, San Andreas fault
• Normal- TENSION force, DIVERGENT boundary- Rio Grande Rift Valley
• Reverse- COMPRESSION force, CONVERGENT boundary- Glacier Natl. Park
• *thrust fault- type of reverse
Hanging and Foot Walls
• Normal and reverse can cause MOUNTAINS and PLATEAUS
• Normal- Fault Block Mountains
• Reverse- Folding forces, mountain range
• Anticlines and Synclines- folding forces that creates arches
Types of Waves
• Focus- where rocks break underground• Epicenter- point on surface above focus• Seismic Wave- p, s, and surface wavesPrimary Waves- Compression/ Longitudinal Waves,
first set of seismic waves, fastest
Secondary Waves- Transverse (horizontally and vertically)
Surface Waves- seen on surface, slowest, transverse
AFTERSHOCK!
Measuring
• What tool do we use to measure these?
• 3 Scales- Mercalli (damage/intensity) , Richter (size of waves, MAGNITUDE) and Moment Magnitude Scale (total energy released)
Volcanoes
What is it?
• A volcano is a weak spot in the crust which allows magma to break through
• Most forms in lines/ belts- ex Ring of Fire
• Magma- in the mantle
• Lava- let loose on the surface
• Most common at DIVERGENT plate boundaries or SUBDUCTION zones
• Divergent boundary- Mid Ocean Ridges, like Iceland and Azores Islands, most stay underwater
• Convergent boundary- Subduction zones, or 2 oceanic plates converging. (In this case- whichever plate is denser due to age, sinks)
• Hot spot- a superheated section of magma blasts through the crust and creates a volcano- exception to rule, not at boundary
Parts of a volcano
How different is lava?
• Temperature and amount of silica (Si +O2)
• More silica THICK LAVA
• Less silica THIN LAVA
• And this determines type of volcano and how it erupts
Eruptions and Stages• 2 types of eruptions- quiet or explosive,
depends of composition and temperature
• Slow eruptions- pahoehoe or aa
• Fast eruptions- pyroclastic flow- ash, cinders and exploding chunks of lava, tephra
• Active, Dormant and Extinct- Erupting, now or soon, might erupt and probably never.
Volcano types
• Shield Volcanoes- thin lava, erupts in layers, low sloped side- ex- hot spots that created Hawaii
Cinder Cone volcanoes
• Steep sided, explosive, thicker lava-ex- Paricutin, Sunset Crater (AZ)
Composite Volcanoes
• Alternates thick and thin lava- therefore explosive or calm eruptions, very tall, generally what you see in pics or diagrams, ex- Mt. Fuji, Mt St. Helens
Lava Plateaus
• Instead of forming a mountain, a plateau is formed instead, thin/ runny lava forms in flat layers- ex- Columbia Plateau
Calderas
• Once a vent runs out of magma, it can become an empty shell-like opening and the mountain collapses in on itself…hmmm…example?
Other weird things volcanoes can do!
• Hot springs- water is heated underground by magma and collects as a pool
• Geyser- water is heated, but let through a small opening which causes pressure and the water sprays out
• Can be utilized for geothermal energy
Also…• Volcanic Neck- magma hardens in the pipe,
jagged landform,
• Batholith- massive chunk of rock forms when magma cools inside of the crust, Yosemite
• Dome Mountain- magma is blocked by rock but it can’t break through, so the rock bends upward, Black Hills, SD
Unique to New Mexico
• Rio Grande Rift
The Earth’s crust thins and pulls apart, a fault. A rift, such as the one here in NM, is considered a continental rift. There are only around 7 on Earth. The Rio Grande helped to make this rift deeper as the Basin and Range Province pulled away from the Colorado Plateau. Where the crust thins- volcanoes form.