2006 Final Section 1&2 Q&A

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Earth & Planetary Sciences
EPSC 201
Anthony Williams- Jones

EPSC201 2006 Final Exam Review Section 1&2 1) Describe the first three minutes of the history of the Universe. At the beginning stages of the universe, energy and mass were constantly changing back and for, via E=mc^2. Once the universe had expanded, and therefore cooled down, matter become much more dominant, than in the early stages. As the universe cools, larger particles are made. Three minutes in; at this point, protons and neutrons are starting collide. There are heavier elements, combinations of neutrons and protons and electrons, being formed. 2) What is the Hubble Constant? How would you use it to determine the age of the Universe? Hubble – asked questions such as: How old is the universe? How fast is it expanding? Will the universe eventually stop expanding and start contracting? Hubble determined our distance from other stars using luminosity of stars. The further a star is, the less luminous is. He used the red shift to determine how fast the stars were moving away from us. He used relative luminosities by comparing different stars. Had to assume every star was the same brightness and speed was constant. He also used groups of stars to account for the fact that their brightness is NOT constant. Using Velocity = Distance / time Hubble was able to predict the age of the universe. He calculated that it was 13.4 billion years old. Current models suggest it is actually 14.67 billion years old – Hubble was very close. 3) Describe and explain the end stages of stellar evolution. Our star was made roughly three and a half billion years ago, and has roughly the same time to live. Our star is middle aged. It is also a 2nd or 3rd generation star. It is in equilibrium where gravity is pulling it together, and fusion is exploding it outward. It’s composition is much different then a 1st generation star, which are much older. The material in the outside of the star has an easier time to overcome gravity and explode outward to become a red giant when nuclear fusion starts to consume most of the hydrogen (3-4 billion years in the future) • Big stars – shorter lifetime • Blue star – 40000 K (think blue wavelength = higher in energy = hotter) Red star – much cooler (red wavelength = shorter wavelength – lower in E = colder) • Proto star – on the verge of becoming a star and burn hydrogen. 4) Sketch a typical seismogram. Explain your sketch. Must be in contact with solid rock. There is a weight attached to a spring, which makes the weight stationary. The frame is bolted to the rock, so when the frame moves the pen marks the paper. The pen is attached to the heavy weight. The second seismograph records sideways motion, the first machine records the vertical motion. A modern day seismograph. As the magnet slides up and down, it records a voltage because its moving in an electric field. 5) What are P and S shadow zones? Explain why they occur. At the core mantle boundary, the P waves are reflected upwards, instead of downwards, which leads to a P-wave shadow zone. This is another line of evidence that there is a liquid outer core. P-wave Shadow zones – seismographs do not record P waves in the shadow zones, this phenomenon is due to the liquid outer core refracting the P waves S-wave shadow zone - also shows there is a liquid outer core. The shadow is much larger. There is also seismic reflection off the dense solid inner core. 6) Describe the essential features of tsunamis and explain why tsunamis occur. Tsunamis – huge waves caused by earthquakes Disturbances of the plates on the ocean floor will cause waves. Not just one wave, but possibly many. It took nine hours from the wave from Japan to hit North America. It takes 13 hours by plane, which means the waves are traveling faster then the plane (over 1000km/h). Extremely fast when moving in the open ocean. In the open ocean, you would hardly notice a wave. Closer to land, the wave is amplified. The wave slows down from 1000 km/h to about 60 km/h but it is much greater in amplitude. Fisherman will notice a tiny wave and not think much of it, and return back to shore to find devastation. By looking at plate movement and past earthquakes, one can predict where the next earthquake will occur. Sea floor displacement propagates tsunami waves. Stuck area will eventually slip and release all the energy at once. Will cause sea floor to bounce up rapidly, causing tsunami waves. Tsunamis in open water have a wavelength of 100,000 meters and are small in amplitude. As they come into shallow water, wavelength shortens, and amplitude
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