GEOLOGY 105 DYNAMIC EARTH EXAM 2025

geothermal energy - Correct Answer-the earth gets hotter the deeper we go -geothermal gradients are steeper in volcanic regions 1) heat is constantly radiating from the mantle 2) heat is produced by radioactive decay of elements 3) heat from magma intrudes into shallow crustal levels the hot dry rock concept heat mining enhanced geothermal systems (EGS) - Correct Answer-1) water is pumped down injection wells 2) picks up heat from hot, fractured rock 3) hot water returns up production wells 4) heat used to drive turbines via heat exchanger 5) produces direct heat for space heating as a by-product 6) cooled water is re-circulated principle of uniformitarianism - Correct Answer-proposed by James Hutton- the geological processes that we see operating today are the same from the past the earth's two dynamic systems - Correct Answer-1) the interior heat engine (primary) - forms ocean basins, mountain ranges, volcanoes and earthquakes 2) exterior heat engine (secondary) - responsible for climate, storms, glaciers, rivers, erosion and sediment geological time - Correct Answer-scientific revolution - the earth is much older than we think it is, deviates from being based on reconstruction of biblical history Hutton's law of superposition - Correct Answer-in an undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it -accumulation rates of sediments are less than a few mm each year Siccar Point, Scotland - Correct Answer--young, flat-lying rocks -unconformity, old folded rocks -means that the earth must be millions of years old how unconformities are produced - Correct Answer--sediments slowly deposit on ocean floor -folded and uplifted into mountains -mountains gradually erode away, making hills, valleys, and then a flat plain -plain sinks below the sea and new sediments are deposited relative age - Correct Answer-determined by the relationship of one rock layer to another absolute age - Correct Answer-obtained from fossil info or radiometric ages using fossils to find ages of rocks - Correct Answer-certain organisms are unique to a certain geological period -DINOSAURS - 280 to 66 million years -TRILOBITE - 570 to 245 million years -AMMONITES - 280 to 66 million years -SHARKS - 500 million years to the present! geochronology - Correct Answer-an absolute method for measuring the ages of rocks, based on the radioactive decay of an unstable parent isotope to a stable daughter isotope the theory of continental drift - Correct Answer--Pangea split into smaller fragments about 200-300 mil yrs ago -formed present arrangement of continents Wegener's interpretation of continental drift - Correct Answer-Pangea was much further south, then broke into two continental masses- Laurasia and Gondwanaland with a tropical sea (Tethys) between them arguments for continental drift - Correct Answer--fit of continents -discrepancy in inferred latitudes of ancient rocks -rocks of same age and similar characteristics on different continents -distribution of similar plants an animals on different continents paleomagnetism - Correct Answer-the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials -the direction and inclination of magnetism of an iron-bearing mineral such as magnetite can tell us where that mineral (or rock) formed with respect to the magnetic pole. conclusions from paleomagnetic evidence - Correct Answer--earth's axis of rotation must have shifted significantly over the last 300 mil yrs (not likely) -OR rocks on the continents are no longer located where they were formed -supports continental drift polar "wandering" curves - Correct Answer-measuring the magnetic direction and inclination recent volcanic rocks from around the world converges on the present magnetic north pole rocks and polar position - Correct Answer--Rocks of different ages give different polar positions -Rocks of the same age but on different continents give different polar positions -The older the rock the further the calculated polar position is from the present position mid-ocean ridges - Correct Answer-underwater mountain ridge system formed by plate tectonics -formed by young volcanic rock (basalt) sea-floor spreading hypothesis (Harry Hess) - Correct Answer-Volcanic eruptions at mid-ocean ridges create new oceanic crust. The newly-formed crust pushes the older crust apart causing the sea-floor to spread. Sea-floor spreading creates the ocean basins, moving the continents apart. magnetic reversals - Correct Answer-once every mil yrs or so the earth's magnetic field reverses itself -counting magnetic reversals provides info on the formation of rocks (like tree rings) Glomar Challenger - Correct Answer-1. The sediment thickness should increase with increasing distance from the ocean ridge. 2. Beneath the sediment there should be volcanic "pillow lavas" exactly like those found on mid-ocean ridges. 3. The age at the base of the sediments should get progressively older with increasing distance from the ridge (so should the age of the lavas beneath the sediments). 4. We should get similar results in all the oceans. subduction zones - Correct Answer-old oceanic crust gets returned to the mantle at the deep ocean trenches -most are found in the pacific ocean -this means the pacific ocean is shrinking and the atlantic ocean is expanding lithosphere - Correct Answer-rigid and is composed of crust and upper mantle, thickness varies from 10-150 km asthenosphere - Correct Answer-soft, plastic and convecting. melting produces volcanic rocks at ocean ridges new lithosphere and oceanic crust is created by ocean ridges by melting of the asthenosphere -Convection in the asthenosphere drives the lithosphere and crust as rigid blocks or PLATES around the surface of the earth. east pacific rise - Correct Answer--this is where new oceanic crust and lithosphere are created -old oceanic crust and lithosphere are subducted at deep ocean trenches (tonga trench and chile trench) benioff zone - Correct Answer-slab of lithosphere descends back into the mantle at a deep ocean trench, earthquakes trace it volcanic island arcs - Correct Answer-produced by melting of the slab when ocean crust is subducted beneath oceanic crust