Earthquakes and Volcanoes

Earthquakes and Volcanoes • Chapter 8 Section 1, pp. 224 - 229 • Chapter 9 Section 3, pp. 260 - 265 • Standard: The relationship between movement of the tectonic plates and major geologic events, such earthquakes and volcanoes

Warm Up: • Explain the 3 types of faults.

EQ: What causes earthquakes? • Seismology • Fault • Deformation • Elastic Rebound • Study of earthquakes • Break in the Earth’s crust along which blocks of crust slide • Change in shape of a rock due to stress • Sudden return of a broken, deformed rock • Energy released as seismic waves

EQ: What are the 3 kinds of faults? • Strike-Slip Fault • Reverse Fault • Transform motion of boundary • 2 Plates slip past each other horizontally • Convergent motion of boundary • Blocks push together, against each other

Normal Fault • NOTE: • Divergent motion of boundary • Blocks pull away from each other • Not all faults are located at plate boundaries • Faults can happen along faults in the middle of a plate

EQ: How do earthquake waves travel? • Seismic waves • P Waves • A wave of energy that travels through the Earth away from an earthquake in all directions • A seismic wave that causes particles of rock to move in a back and forth motion.

Waves Continued: • S Waves • Body Waves • Surface Waves • A seismic wave that causes particles of rock to move in a side to side direction. • Travel through Earth’s interior • Travel along Earth’s surface

Ticket out the Door: • Which wave is most damaging? Explain and support your answer.

Warm Up: Are their different types of earthquakes? Explain.

EQ: How are earthquakes measured? • Seismograph • Epicenter • Focus • Instrument that records seismic waves • The point on Earth’s surface directly above an earthquake’s starting point • The starting point along a fault

Richter Magnitude Scale • Measure the strength of an earthquake on a 0 – 10 scale • Measure ground motion or magnitude (strength) • For each 1 unit of magnitude , ground motion increases 10 times

Intensity of an Earthquake • A measure of the degree to which an earthquake is felt by people and the amount of damage caused.

Summary • What do you think is the reason Georgia does not have many earthquakes?

EQ: What is a Volcano? • Volcano is a vent of fissure in the Earth’s surface through which magma and gases are expelled. • Magma is molten rock forced to the Earth’s surface • Lava is magma that flows onto the Earth’s surface

EQ: What are 2 types of Volcanic Eruptions? Non-Explosive: • The most common type of eruption • Produces relatively calm flows of lava • Found in much of the seafloor, Northwest regions of the US, & other vast regions on Earth’s surface • Examples: Mauna Loa & Kilauea in Hawaii

EQ: What are 2 types of Volcanic Eruptions continued: Explosive: • They are rare, but very destructive • Clouds of hot debris, ash, and gas repeatedly shoot out of the volcano • Pyroclastic flows erupt from the volcano producing molten rock, which hardens in the air, and dust sized particles of ash. The ash can reach the upper atmosphere and circle the Earth for years. • The lava and large pieces of debris are blasted out of the volcano in a matter of seconds. This can demolish an entire mountainside in seconds. • Example: Mount St. Helens in Washington state

Shield Volcanoes • Built of layers of lava released from nonexplosive eruptions. • Lava is very runny • Layers of lava create a volcano with sloping sides • Not very steep sides, but can grow to be enormous • Tallest Mountain on Earth: Mauna Kea in Hawaii

Mauna Loa (in Hawaii)

Cinder Cone Volcanoes • Made of pyroclastic material from moderate eruptions • Steep sides • Small volcanoes • Erupt for short periods of time • Often occur in clusters on sides of volcanoes • Erode away quickly because pyroclastic material is not cemented together • Paricutin~Mexican volcano appeared in a cornfield in 1943 and erupted for 9 years

Cerro Negro (in Nicaragua)

Composite Volcanoes • AKA: Stratovolcanoes • One of the most common types of volcanoes • Form from explosive eruptions of pyroclastic material followed by quieter lava flows • Lava and pyroclastic material form alternating layers • Broad bases and steeper towards the top • EX: Mt. Hood, Mt. Shasta, Mt. Ranier, and Mt. St. Helens (all in US); Mt. Fuji is in Japan

Mount St. Helens (Washington state)

EQ: How does magma form and move? • Formation of Magma • Forms in the lower crust & upper mantle • Caused by changes in heat & pressure • Usually the result of decrease pressure • Rises to the surface since magma is less dense than rock • Usually, at plate boundaries Ex: Ring of Fire In Pacific Ocean

EQ: Where do volcanoes form? • @Rift Zones • Deep cracks between divergent plates, like the Mid-Ocean Ridge in the Pacific & North Atlantic Oceans • Remember Sea Floor Spreading

@Convergent Boundaries/Subduction Zones • At oceanic & continental plates • Oceanic crust subducts under continental crust • Oceanic water mixes with the mantle rock, melts it & allows magma to rise

@Hot Spots • Volcanically active areas far from plate boundaries • Example: Hawaiian Islands

EQ: How does a Scientist Predict a Volcano is going to Erupt? Classified in 3 categories • Extinct: has not erupted in recorded history and probably will never erupt again • Dormant: currently is not erupting, but the record of past eruptions suggests the volcano will erupt again • Active: currently erupting or shows signs of erupting again in the near future

Summary • Explain how an earthquake can set off a volcano?

Earthquakes and Volcanoes