Earth Science
Question 1
What unlikely feature formed along the fault scarps of Central California?
The Salton Sea
Wallace Creek
Sag ponds
Pinnacle National Park
Question 2
What two plates interact to form the San Andreas Fault?
Pacific plate and Nazca plate
North American plate and Pacific plate
North American plate and Cocos plate
Pacific plate and Caribbean plate
Question 3
When was the last big Earthquake along the main fault?
1989
2011
1906
1871
Question 4
In which direction does Wallace Creeks offset?
Northwest
Southwest
Southeast
Northeast
Question 5
When did the San Andreas Fault appear?
28 million years ago
50 million years ago
28,000 years ago
50,000 years ago
Question 6
The San Andreas Fault is called a:
Right lateral strike slip fault
Transform dip-slip fault
Right dip-slip fault
Transform strike slip fault
Question 7
What is an example of this plate movement?
The separation of California and Baja California
Rocks of Pinnacles National Park match those of Antelope Valley, nearly 200 miles away
The northward flow of rivers along the San Andreas fault
The Salton Sea
Question 8
Why do mountains form around Big Bend?
Magma surfaces when the San Andreas Fault creeps.
The bend in the fault causes this area to be bound, squeezed, and uplifted.
The fault is raised here.
Fault creep creates pressure, causing uplift.
Question 9
In your own words, what creates Earthquakes? (75 word minimum)
Earthquakes occur in areas where there are weak fault lines underneath the earth’s surface. Tectonic plates are always moving, albeit slowly. When two plates collide, vibrations occur which travel outwards as seismic waves. This causes the ground to shake. Another way earthquakes occur is when two plates move alongside each other, but in the process become stuck due to friction. When the plates overcome the force of friction at the edges, sudden pressure release occurs, which causes vibrations that travel as seismic waves (Hung et al., 2010). The seismic waves also travel laterally as well as downwards.
Reference
Hung, C. J., National Highway Institute (U.S.), & Parsons, Brinckerhoff, Quade & Douglas. (2010). Technical manual for design and construction of road tunnels–civil elements. Washington, D.C.: U.S. Dept. of Transportation, Federal Highway Administration, National Highway Institute.
ASSESSMENT
number nine
Recall from reading the nature of volcanoes, and in your own words, briefly discuss how the rate of cooling determines the type of rock that forms from magma/lava.
The rate of cooling significantly determines the type of rock that form from magma (Owings, 2015). When magma cools, it forms igneous rocks. The rate of cooling determines the crystal sizes of the igneous rocks. When lava flows to the surface, it cools quickly, leading to formation of small crystals. This leads to formation of obsidian and basalt rocks also known as extrusive igneous rocks. When lava cools slowly (for instance underground lava), large crystals develop. This leads to formation of igneous rocks such as gabbro and granite that comprise of large crystals.
number ten
Recall from your reading about the nature of volcanoes, and in your own words, compare and contrast aa and pahoehoe lava in appearance and how they form
Aa and pahoehoe are the major forms of basaltic lava flow. A major difference between the two is that pahoehoe appears smooth and is viscous in texture, while aa has rough surfaces. Rapid lava flows characterize aa formation, while pahoehoe is characterized by low velocity flows. Aa has higher viscosity while pahoehoe has lower viscosity (Owings, 2015).
Reference
Owings, L. (2015). Igneous rocks. Abdo Publishing.
number eleven
In your own words, briefly explain how a caldera forms from principle types of volcanos
A caldera may form in two principle ways, which include violent volcanic eruption and from collapse of the surface rocks around a void lava chamber (Gottsmann & Martí, 2008). Violent volcanic explosions occur in magma comprising silica that is highly viscous. As the lava rises, trapped gas bubbles expand due to reduced pressure. When they reach close to the vent, a violent explosion may occur, throwing large pieces of rock away. This may leave the water table exposed or water may collect in the area. This leads to formation of a caldera. Collapse calderas occur when a magma chamber undergoes eruption and is left empty. This leaves rocks on the edges of the chamber hanging. With time, they collapse under their own weight into the chamber, forming a wide caldera.
Reference
Gottsmann, J., & Martí, J. (2008). Caldera volcanism: Analysis, modelling and response. Amsterdam: Elsevier.
number twelve (two hundred words)
In your own words, discuss volcanic hazards. Although commonly thought to be associated with most volcanic eruptions (by the general public), lava is rarely responsible for the loss of life. Which hazards would tend to be more deadly? Finally, indicate and discuss those hazards that are a direct result of a volcanic eruption as well as those hazards that are indirectly linked. (Hint: think of “indirectly associated” hazards as “side effects”.).
There are various volcanic hazards that may impact people during eruptions. One of the volcanic hazards is debris-flow avalanches. This may occur when over steepened volcanoes collapse, causing a debris flow over the steep slopes of the mountain. The avalanches may endanger lives of those living near the eruption point. Another hazard is pyroclastic falls that comprise of tephra and other projectiles. These include debris of various sizes that are projected at great velocities (Loughlin et al., 2015). Falling debris may be dangerous to people and property. Another hazard involves the various gases that may be released during an eruption. Common gases include water vapor, fluorine, sulfur oxides, carbon monoxide, chlorine, and hydrogen sulfide. Another hazard is pyroclastic density currents that comprise of a mixture of ash, hot gases, and rock dust. These currents can move in the air at great speeds causing death and destruction.
Lahars is another common hazard around volcanoes. Lahars may occur when volcanic flows encounter water or ice (Loughlin et al., 2015. When volcanic flows mix with water or ice, they can move through valleys at higher speeds causing destruction. Direct hazards from valcanoes include gases, pyroclastic falls, pyroclastic density currents, and lava. These can cause death and destruction directly. For instance, pyroclastic currents and falls may injure people by falling on them and causing physical harm (Loughlin et al., 2015). Indirect hazards include debris-flow avalanches, lahars, and destruction of the natural flora and fauna of the environment. This may lead to famine especially where crops are destroyed.
Reference
Loughlin, S. C., Sparks, S., Brown, S. K., Vye-Brown, C, Jenkins, S. F. (2015). Global volcanic hazards and risk. Cambrige: Cambridge University Press.
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