Alfred Wegener came up with the idea of continental drift in 1912. He stated that there was once one large landmass called Pangaea that broke apart about 200 million years ago. Continental drift is the idea that the continents have drifted slowly over time to their current locations.

Continental Drift Theory: Evidence to support Continental Drift Theory:   1)  puzzle-like fit of the continents 2)  fossil evidence 3)  climate clues 4)  rock clues 5) earthquake/volcano data 6) sea-floor spreading * sonar map of sea floor * dating of sea-floor rock samples * paleomagnetism

Fossil Evidence Similar plant and animal fossils are found around different continent shores, suggesting that they were once joined.

Climate Clues Fossils have been found in Antarctica of plants that can only live in tropical climates so at one point it must have had a tropical climate. The Climate changed because the island moved!

Rock Evidence (Landforms) The discovery that similar rock formations and mineral deposits match up along coastlines of different continents. Certain rocks such as coal only formed in hot climates but were found in cold regions. There is similar mountain building along coastline of different continents.

Sea-floor spreading Scientists found a system of ridges and valleys throughout the ocean floors. In the 1960s scientist Harry Hess suggested the idea known as sea-floor spreading. Mid-Atlantic Ridge

Sea-floor spreading 1) Hot, less dense material in the mantle is forced upward to the surface at the mid-ocean ridge. 2) It then turns sideways, carrying the seafloor away in both directions.

Sea-floor spreading 3) Magma under the sea-floor flows up into the cracks and hardens to create a new seafloor. 4) The old seafloor gets hard and sinks to create a valley.

Magnetic polarity at mid-ocean ridge

The crust of the Earth is broken into large segments or pieces called tectonic plates.

What causes tectonic plates to move? A convection current is occurring in the mantle. * Hot, less dense liquid magma rises to the top of the mantle. * As it cools it gets heavy and sinks back down.

Convection currents

Types of Tectonic Plate Boundaries

Divergent boundaries * two plates are moving apart from each other * Example- sea-floor spreading at Mid-Atlantic ridge

2) Convergent boundaries * two plates are moving toward each other; two plates collide * Subduction zone- two plates collide and one goes under the other and melts. * mountains are created when two plates collide

Subduction Zone

3) Transform boundaries * two plates slide past one another in opposite directions * earthquakes can occur when this happens

VOLCANISM

VOLCANISM: All processes associated with the discharge of magma, hot fluids, and gasses

Volcano- a mountain that forms when layers of lava and volcanic ash erupt and build up. * most volcanoes on Earth are dormant (not active) *There are about 600 active volcanoes on Earth.

Magma- molten (melted) rock that is located beneath the Earth’s surface. The more silica magma contains the thicker it is. Lava- magma that flows to the Earth’s surface. lava magma

What types of tectonic activity cause volcanoes to occur?

Divergent boundaries * When 2 plates are moving apart, it creates an opening or ridge. * Magma flows into the ridge and is cooled by sea water. * pillow lava * non-explosive

2) Convergent boundaries- * Magma created in the subduction zone is forced upward because the HOT magma is less dense than cooled rock of the surrounding crust. * example: Mount St. Helens in Washington State

Formation of a volcano at subduction zone

TWO major belts (volcanoes at convergent boundaries): Circum-Pacific (Ring of Fire) * Pacific plate 2) Mediterranean Belt: * Eurasian, African, & Arabian plates 34

Pacific Ring of Fire

Mediterranean Belt 36

3) Hot Spots- * Some areas of the mantle are hotter than others. These areas are called hot spots. * These hot spots melt rock which is forced upward to the Earth’s crust.

Yellow Stone National Park

* Example- Hawaiian Islands Hot Spots- OCEANIC * As the plates move over the hot spot, many volcanic islands may form. * Example- Hawaiian Islands 41

A chain of island volcanoes can form at a hot spot.

Hot Spots- CONTINENTAL * Flood basalts form when lava flows out of long cracks in the Earth’s crust called fissures. * This lava flow results in flat plains called plateaus. * Ex: Columbia Plateau in Washington & Oregon 44

Three types of volcanoes                                                                                                                                                                                                                                                 

Shield volcano- * quiet eruptions * slow-moving, non-viscous lava flows out in flat layers (low silica content) * creates a broad volcano with gently sloping sides

Shield volcano                                                                                                                                         

2) Cinder Cone Volcano- * explosive eruptions that shoot lava high into the air (thick, viscous lava that has high silica content) * lava then falls back down and cools * this creates a small, steep-sided volcanic mountain (cone shape)

Cinder- Cone volcano

3) Composite volcano (stratovolcano)- * both explosive and quiet eruptions * First, an explosive period shooting up lava. Then, a quiet period of slow moving lava flows. * large, steep-sided and symmetrical built of layers of ash and lava

Composite Volcano

ERUPTION! The type of eruption is determined by the composition of magma. Temperature Pressure Presence of water Amount of silica

AMOUNT OF SILICA high silica= high viscosity traps gasses EXPLOSIVE!! low silica= not viscous easy flow QUIET & NON-EXPLOSIVE!!

Three Types of Magma Basaltic Andesitic Rhyolitic

Anatomy of a Volcano Ash cloud Crater Vent Conduit Magma Chamber

Anatomy of a Volcano

Anatomy of a Volcano

CRATER Bowl-shaped depression formed around the vent, Less than 1 km in diameter VS. CALDERA Larger depression, can be up to 50 km in diameter, often forms when top or sides of the volcano collapses into the magma chamber

Eruption of a Volcano Terms to know: Tephra Pyroclastic flow Lahar

Types of Lava Aa: forms from cooler, thicker lava. Hardens into a rock with a rough, jagged surface

Types of Lava Pahoehoe: formed from thin, runny lava. Hardens into a rock with a smooth, rope-like surface.

Pillow lava: lava formed from eruptions under water Types of Lava Pillow lava: lava formed from eruptions under water

Pillow lava: lava formed from eruptions under water Types of Lava Pillow lava: lava formed from eruptions under water

Extinct: volcano that is unlikely to erupt again Volcanoes can be….. Active: a volcano that is erupting or shows signs that it will erupt in the near future Dormant: volcano that scientist expect to awake in the future and become active Extinct: volcano that is unlikely to erupt again

EARTHQUAKES

is the force that acts on rocks to change the shape of volume Stress- is the force that acts on rocks to change the shape of volume

3 Types of Stress

Tension > plate pulling apart (divergent boundary) > The rock of the crust thins in the middle > The thin rock in the middle acts like warm bubble-gum.

2) Compression > Plate converging (convergent boundary) > Plates are pushing into each other > Squeezes the rock until it folds or breaks

3) Shearing > Two plates at a transform boundary > Pushes a mass of rock in opposite directions > Rock can break and slip apart OR change shape

earthquake- is the movement of the ground caused by waves from energy released as rocks move along faults

facts: Most earthquakes occur along tectonic plate boundaries 80% of all earthquakes occur along the edges of the Pacific Plate. (Pacific Ring of Fire)

A fault is a large crack in rocks. The rocks not only crack but move along side each other.

3 Types of Faults

Normal Fault Reverse Fault (Thrust Fault) Strike-slip Fault Foot Wall Hanging Wall Reverse Fault (Thrust Fault) Strike-slip Fault

Normal faults- (Divergent Boundary) Tension The hanging wall (fault surface) moves DOWN This type of fault created the Sierra Nevada Mountains

2) Reverse fault- (Convergent Boundary) Compression Hanging wall (fault surface) moves UP This type of fault movement created the Himalaya Mountains of India.

3) Strike-Slip Faults- (Transform Boundary) Shearing Rocks on either side of the fault surface are sliding past each other Transform boundary When the pressure and stress builds up as the rocks move past each other, eventually they will break resulting in an earthquake.

3 types of faults Name ________________ Date______ period _____ A __________________ B. __________________ C. __________________ B C