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.