Volcanoes and Earthquakes Eric Angat Environmental Science

Essential Questions How do I describe the relationships between plate boundaries, volcanoes, and earthquakes?

1.What is the theory of Plate tectonics? (07:08) P Een 2.1.1

Seafloor spreading explains why the oldest part of the ocean floor is found farthest from the mid-ocean ridge. Alfred Wegener called the large supercontinent that once existed as Pangaea. Scientists believe that tectonic plates move because of the convection current in the mantle. Een 2.1.1

2. How do the continents move?

The Earth's crust is divided into large slabs of rock that drift and collide together because of the convection current in the asthenosphere ( mantle ). These slabs of rock are the tectonic plates. Een 2.1.1

San Andreas Fault, California

3. Why are earthquakes common in the California and Alaska? Think!

4. Complete concept map. P-waves S-waves back and forth Right angle rolling Use the following words. Een 2.1.1

P-waves S-waves back and forth Right angle Rolling motion

5. How are buildings designed to withstand earthquakes? (01:47) P-waves are earthquake waves that travel the fastest and arrive at a location first. The process of making structures, such as buildings and bridges, stronger against earthquakes is called seismic retrofitting Een p. 511

Energy released during an earthquake creates seismic waves. Earthquakes usually occur along tectonic plate boundaries, especially in the Pacific Ring of Fire. Een 2.1.1

6. What is a fault and how does it cause an earthquake? Think! Fault is a break on earth crust where pressure builds up. When this pressure is released an earthquake happens. The sudden movement generates an earthquake at a point called the focus. The energy from the earthquake spreads out as seismic waves in all directions. The epicenter of the earthquake is the location where seismic waves reach the surface directly above the focus.earthquakefocusseismic waves

Slab pull in the Subduction zone

Seismic waves travel in all directions.

Tsunamis are mostly undetectable in the deep oceans.

7. Why does Earth’s temperature drop when volcanoes erupts? Illustrate and explain your answer. P. 490 Een 2.1.2

Pyroclastic cloud

8. Draw and describe a Composite Volcano. P The most dangerous volcanoes are composite volcanoes. Why? Een 2.1.2

9. Draw and Describe a Cinder Cone Volcano. (01:54) P Een 2.1.2

10. Draw and describe a Shield Volcano. (02:05) P Een 2.1.2

Mauna Kea (left) and Mauna Loa (right), both over 4000 m above sea level, are the world's largest active volcanoes, rising nearly 9 km above the sea floor around the island of Hawaii. This aerial view from the NW shows the contrasting morphologies of these two shield volcanoes. In contrast to the smooth profile of Mauna Loa, Mauna Kea's early shield volcano morphology is modified by the late-stage products of explosive eruptions. Photo by Lee Siebert, 1987 (Smithsonian Institution).

The Ring of Fire refers to the volcanoes surrounding the Pacific Ocean Subduction zones occur all around the Pacific Ocean basin. This entire region is known as the Ring of Fire. The Hawaiian Island chains were formed by a hot spot Een 2.1.2

11. What are effects of a volcanic eruption? P Een Pyroclastic materials Tephra Lava Lahar Acid rain from sulfur Earthquake Landslides (mass movement)

PositiveNegative The dramatic scenery created by volcanic eruptions attracts tourists. This brings income to an area. Many lives can be lost as a result of a volcanic eruption. The lava and ash deposited during an eruption breaks down to provide valuable nutrients for the soil. This creates very fertile soil which is good for agriculture If the ash and mud from a volcanic eruption mix with rain water or melting snow, fast moving mudflows are created. These flows are called lahars. The high level of heat and activity inside the Earth, close to a volcano, can provide opportunities for generating geothermal energy. Lava flows and lahars can destroy settlements and clear areas of woodland or agriculture. Human and natural landscapes can be destroyed and changed forever.

12. How do granite ( igneous) rocks form? (05:01) p. 117

oceanic-oceanic boundary Ocean Subduction Island Arc Ocean When two oceanic crust collide subduction happens and the melted crust rises to form a volcanic arc.

Oceanic – oceanic convergent boundary

oceanic-continental boundary An oceanic plate is heavier than a continental plate that is why it sinks under the continental plate. oceanic plate continental plate. Subduction

Oceanic – continental convergent boundary

ocean ridge or mid ocean ridge This is happening in the Atlantic ocean. The oceanic plate is diverging ( moving apart) and the gap is filled by cooled lava forming basalt. The Atlantic ocean is widening by about 2-3 cm. or 1 inch every year.

ocean ridge or mid ocean ridge The oldest sea floor is the one farthest from the ridge and the youngest sea floor is the one nearest to the ridge. oldest youngest

continental-continental boundary When two continental crust converge. A mountain range is formed. An example of this is the converging plates of India and Asia, where Himalayas is still forming (Orogeny- mountain building).

Continental-continental convergent boundary

A transform boundary exists where one of the Earth's plates slides past another plate Evidences that Earth's surface consists of plates that are in continuous motion include earthquakes, mountains, and volcanoes.

The San Andreas fault is an example of strike-slip fault. The San Andreas fault is an example of transforms or sliding boundary. The San Andreas fault is an example of shear stress Een 2.1.1

LandformLocation Type of fault Type of boundary Type of stress San Andreas Fault strike -slip fault. transforms or sliding boundary shear stress Anatomy of the San Andreas Fault

Een 2.1.1