Geology Quiz #1

Where did most of the mid-20th century observations that brought geologists back to Wegener's ideas come from? Describe three of those observations.

Most of the mid-20th century observations that brought geologist back to Wegener's ideas were due to new technology made for exploring the sea floor. For example, the discovery of mid-ocean ridges. Also, they discovered that rock on the seafloor is composed differently that continental crust. In addition, they discovered that there is only a very thin layer of sediment cover on the seafloor, when they thought it was thick. This led to them discovering that the seafloor is very young compared to the continental crust.

Describe two lines of evidence that led scientists to believe the earth is layered.

One line of evidence that led scientists to believe there were layers was studies that provided the estimate of the earth's average density. They found that the density was about 5.5 gm, but since the surface density is only 3.0 gm they realized that the interior of the earth must contain denser material. Another line of evidence was that since the earth is nearly sphere scientists decided the metal must concentrate near the middle thus making up the core.

Describe two different scenarios outside the classroom in which your understanding of geologic processes would help inform your decision-making.

One scenario would be researching where you would build a house, if you were to build a house on a hill you would want to make sure the hill was stable. Understanding the physics of geology would help insure that your house won't slide off the hill because of weather or any other circumstances. Another decision-making process would be if you're moving you might not want to move to the west side of the United States if you are not a fan of earthquakes.

What is Moho? What advances led to its discovery

The Moho is the boundary between the crust and mantle. What lead to the discovery of it was when a researcher discovered that tens of kilometers below the surface of the continental crust that the seismic waves increased in speed, which he suggested was because of a change in the properties of the rock.

Compare and contrast the crust and the mantle.

The crust and mantle are both considered compositional layers. The crust is the first layer of the earth, the top layer on which we live on. It is solid, consists of the continental crust (25-75 km) and oceanic crust (6-10 km) and contains the least iron. The mantle (2900 km) is the second layer of the earth, and contains more iron than the crust.

Compare and contrast the crust and the lithosphere.

The crust is part of the lithosphere. The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks, not as dense rock. Two types of crust, continental (25-75 km) and oceanic (6-10 km). Lithosphere is all of the brittle rock exterior to the asthenosphere.

Contrast the plate tectonic environment of the east and west coasts of the United States.

The plate tectonic environments differ on the east and west coasts of the US because of where they are located on a plate. The west coast is located on a convergent plate boundary so it is considered active. This means that there are more eruptions, earthquakes, and mountains formed. The east coast is located on the interior of a plate that spans out to the middle of the Atlantic Ocean. Since it's located on the interior it's considered a passive environment and it has relatively less activity.

Describe the difference between the convergent margin that exists here in the Pacific Northwest and the one that exists between India and the rest of Asia.

The plate that is here in the Pacific Northwest is active and there is still plate movement occurring because since the other plate meeting it has seafloor crust which means it is still able to move under the North American plate. The one that exists between India and the rest of Asia has stopped moving since the plate that India was on ran out of seafloor crust to move under the other plate it was approaching and when it finally got to the continental crust it pushed a lot of rock, forming the Himalayan mountains. This also caused the plate to stop moving.

Write a brief, simple outline of the theory of plate tectonics.

The theory of plate tectonics states that the surface layer of the earth (the lithosphere) is broken into large pieces called plates. The plates move continuously and independently. Plate edge interactions like convergent, divergent, or shearing plates cause geologic action such as earthquakes, mountain forming, and eruptions. Compared to plate edges, the interiors are relatively quiet.

List and describe the three basic types of plate edge interactions and give a specific geographic example of each.

The three basic types of plate edge interactions are convergent margin, divergent margin, and transform/ shearing margin. Convergent margin is when two plates start pushing into each other, causing either a subduction zone where one plate slides beneath another or a collisional boundary where the plates collide and therefore push each other upward, a good example of this is the Pacific Northwest and the mountain range we have. Divergent margin are plates moving away from each other, like the Mid-Atlantic ridge. Transform or Shearing margins are when the tectonic plates slide past each other leaving something like the San Andreas Fault.

Describe three lines of evidence cited by Alfred Wegener in support of his hypothesis of continental drift.

-Jigsaw puzzle fit of continents (PANGEA) -You can find some fossils across many continents -Rocks and rock structures match across continents -Evidence of paleoclimate- rocks that are associated with particular kinds of surface conditions

How do hypotheses and theories in science differ from one another?

A hypothesis is a possible explanation, involving only natural processes, that can explain a set of observations. However, a theory is a scientific idea supported by an abundance of evidence. They have passed every test and scientists are much more confident in the correctness of a theory.

Explain the paleomagnetic evidence for either sea-floor spreading or apparent polar wandering.

Apparent Polar Wandering: At first, when scientists discovered apparent polar wandering they figured that they assumed that the apparent polar-wander path represented how the position of Earth's magnetic pole really migrated over time. But then when they obtained polar-wander paths from many different continents, they found that each continent has a different apparent polar- wander path and that it was the continents that were moving and not the earth's magnetic pole.

Explain why chemistry and physics are so important to geology.

Because Geology is the study of Earth's physics, chemistry, and history. Geology is related to how the parts of the Earth move which is directly related to physics. It also has to do with chemical reactions occur within and between different rocks, minerals, and other elements of the Earth's geology relate to chemistry.

Why did the scientific community reject the hypothesis of continental drift? Include both the trivial and the scientifically important reasons in your answer.

Because he was a German born in South Africa talking to American and British geologists at the time of WWI. He was a meteorologist. He had no explanation for how the plates of the Earth moved from their original position as one when they were Pangaea because they're so heavy and it made no sense.

Compare and contrast the lithosphere and asthenosphere.

Both the lithosphere and the asthenosphere contain part of the mantle and they are both behavioral layers of the earth's internal structure. The lithosphere is the layer that contains the crust and part of the mantle. It is characterized by being composed of rock that is brittle and breaks easily. The asthenosphere is the next layer that contains part of the mantle. It is characterized by being composed of rock that is ductile.

Explain how a convergent plate boundary "dies" (in other words, how and why does a convergent boundary "stall out" and slowly cease to subduct lithosphere?)

Convergent plate boundaries cease to subduct lithosphere when two pieces of continental crust collide into each other and since neither subduct, push up to make mountain ranges. The continental crust is too buoyant to subduct into the lithosphere. For example when the convergent plate boundary between India and Asia caused them to collide, the Himalayan mountains were formed.

Describe three geologic features or events that are common at plate edges but uncommon elsewhere.

Earthquakes occur at these plate edges because of the movement and friction that occur at these points. Mountains and volcanoes are also formed at these plate edges from where two plates come together and the rock is pushed up. Drenches can also occur along plate edges like the one on the San Andres Fault.

Describe three specific aspects of Earth's processes a geologist might study.

Groundwater, its movement, and its reaction with rock and soil. Volcanic eruptions and their product. Earthquakes and the Earth's interior as revealed by earthquake waves.