EAR 110 3rd EditionExam # 1 Study Guide Lectures: 1 - 7Lecture 1 (January 13)The Nature of GeologyDescribe one example of how geology affects where we live. Answer: Geology affects where we live because it affects topography, including features such as steep cliffs and valley floors with good soil. Geology affects how safe or unsafe a place is to live in. For example, it is not very safe to leave near volcanoes or faults because these are geologically active areas. List the main layers of earth’s subsurface in order from the surface to the center.Answer: The layers of Earth are the crust, the upper mantle, the lower mantle, the outer core, and the inner core. Why is the inner core solid, but the outer core liquid?Answer: The inner core is solid because there is more pressure at the center of the earth. This pressure decreases the melting point of the iron/nickel alloy and it remains in a solid state. What are some differences between continental and oceanic crusts?Continental crusts tend to be thicker, less dense, and made of granite. Oceanic crusts tend to bethinner, denser, and are made of basalt. Lecture 2 (January 15) The rock conglomerate is made of different sized particles that are not well sorted. Was it madein a high energy or low energy environment?Answer: High energy environments do not have well sorted particles, such as the face of steep mountain slope, so we can infer conglomerate was made in a high energy environment. Which volcanic eruptions are less dangerous: those with low silica content or high silica content?Give one example of each type of eruption.Answer: Low silica content eruptions are less dangerous. These eruptions are more fluid, like the lava flows of Hawaii. A high silica eruption has a lot of ash and can be very dangerous, like Mount St Helens. What do some igneous rocks have small grains while others have large grains?Grains take time to grow, so rocks with small grains cooled very quickly on the surface of Earth and grains did not have time to develop. Rocks that cool slowly beneath the Earth’s surface have larger grains because the grains had time to develop and grow. What is the difference between an igneous and metamorphic rock?Igneous rocks are formed from the solidification of magma and metamorphic rocks are formed from intense heat and pressure. What are the four spheres of Earth?The four spheres are the atmosphere, biosphere, hydrosphere, and lithosphere. Lecture 3 (January 20)What is lithification?Lithification is the process of forming rocks. What do contours show on a topographic map? What does it mean if contour lines are close together?Contours represent lines of equal elevation, so they show areas that have the same elevation. Close contour lines indicate steep topography such as a mountain. How can the Principle of Original Horizontality be used to age rock layers?The Principle of Original Horizontality states that layers of rock were deposited flat (horizontal) on top of one another, so the oldest rocks are at the bottom and the youngest are at the top. Why are faults and intrusions younger than the layers of rock they are found in?The layer of rocks must have existed before the fault/intrusion occurred, therefore the layer of rocks are older. Lecture 4 (January 22)What is the difference between a cross section and a stratigraphic section?Both a cross section and stratigraphic section show the subsurface geometry of rock (layers and thicknesses of layers), but a cross section also shows topography. Give one example of qualitative data and one example of quantitative data that can be obtainedin the field. Qualitative data can include a sketch of the landscape or recording the color of rocks. Quantitative data in the field can include measuring the angle of cliff or the temperature of a lava flow.Which geologic era are we currently in? When did it begin?We are currently in the Cenozoic Era which began 65 million years ago. In what geologic era did the first flowering plants and dinosaur appear?The Mesozoic Era, which began 251 million years ago. What is a geologic period? How many are there?A geologic period is a subdivision of a geologic era. There are 12 geologic periods over the 4 geologic eras. Lecture 5 (January 27th)Why does the earth have large fracture systems?The earth is curved – the cold, rigid rock at the bottom of the ocean floor can’t bend well and cracks, forming fracture systems.What kinds of evidence did Wegner use to support his theory of Continental Drift?1) The shapes of the continents (South America and Africa)2) Similar fossils found on continents now separated by oceansWhat are some global patterns that are evidence for plate tectonics?1) Pattern of earthquakes (in distinct belts along plate boundaries)2) Pattern of volcanoes (also in distinct belts along plate boundaries)3) Pattern of mountain melts (also in distinct belts)What are the three types of plate boundaries and the relative motion of the plates?Convergent (moving towards each other), Divergent (moving away from each other) and transform (moving horizontally past one another)Lecture 6 (January 29)How do oceanic-oceanic convergent boundaries form volcanic island arcs?When the two plates collide, one is subducted underneath the other. When the plate is subducted, it releases water which lowers the melting point of the rock and causes melting. This melted magma rises to the surface and erupts to form volcanoes. Why do continent-continent boundaries have few volcanoes?Both continental plates are buoyant and subduction does not occur. Without subduction, there is no melting of magma. Which types of plate boundary can link spreading segments in the mid ocean ridge?Transform boundariesName two forces that cause the plates to move. Which is the dominant force?1) Slab pull (dominant force)2) Convection currents in the mantleHow can rocks be used to tell the direction of the magnetic field in the past?As a rock forms, the crystals within the rock cool and solidify pointing toward magnetic north at the time the rock was formed, so we can use this information to tell where magnetic north was at the time by dating the age of the rock. What evidence is there for plate tectonics on the ocean floor near spreading centers?1) Age of Rock: rocks are youngest near mid ocean ridges and increase with age as you move away2) Sediment thickness is thinnest near the mid ocean ridges and increases as you move awayLecture 7 (February 3rd)What