Download Unit 7 Study Guide Answer Key

Unit 7 Study Guide Answer Key
I. Earth’s Interior
1. The three main layers of the Earth are the Crust (thin, rocky outer layer), the
Mantle (thick layer of hot, but solid rock), and the Core (a large sphere of
metal that occupies the Earth’s center.)
2. The Lithosphere is a layer of relatively cool rigid rock that include the upper
most mantle and the Earth’s crust. The Asthenosphere ia a layer of softer
weaker rock that can flow slowly, the way taffy does. The Mesosphere is
the stronger, stiffer lower part of the mantle.
3. The two types of crust are Continental crust (which is less dense, mostly
granite and is under the Continents) and Oceanic crust (which is more
dense, mostly basalt and…..wait for it……shockingly under the oceans)
4. did not cover…..not a GSE
5. A geologist is a scientist who studies Earth and the processes that have shaped
Earth over time.
II. Plate Tectonics
6. The “Theory of Plate Tectonics” is the theory that pieces of the Earth’s
lithosphere, called plates, move about slowly on top of the asthenosphere.
Evidence to support this includes: the mid-ocean ridge, sea-floor spreading,
and subduction of oceanic plates.
7. New sea floor is formed at a mid-ocean ridge as the two plates move away
from each other (Divergent Boundary). When this happens, magma wells up
and then solidifies to form new crust.
8. The force that powers the movement of the continents is the convection
currents in the mantle (asthenosphere).
9. Convergent---collide…….Divergent ---divide……Transform tectonic plates
slide.
(admit it…..you’re singing the song now )
10. Most mountains form at convergent boundaries of two continental crust
pieces. They form as the crust pushes together and folds itself upward.
11. Old oceanic crust is not really destroyed, it is recycled. This happens at
convergent boundaries where the oceanic plate is subducted under the
continental one. The oceanic plate re-melts into magma.
12. Trenches are usually located at the edge of a convergent boundary with
subduction. This is because the more dense plate (oceanic) sinks down below
the continental plate (less dense) and pulls down the front edge of the
continental plate.
III. Earthquakes and Volcanoes
13. Before an earthquake occurs stress build op along the fault due to the fact that
the crust on the two different sides of the fault are trying to move in different
directions. When the earthquake occurs, the stress/ pressure is released.
(think about dragging the wooden block across the sandpaper last year)
14. Earthquakes occur most often at Transform boundaries. They also occur at
other types of boundaries as well as fault lines.
15. Volcanoes form at hot spots (like Hawaii) as well as near Subduction Zones.
They happen because magma from the mantle rises up through the crust.
16. As more and more magma collects, pressure builds under ground. When the
pressure is too great, it needs to be released. This release happens through the
eruption of a volcano.
IV. Rock Cycle
17. The rock cycle is a series of processes in which rocks continuously transform
from one type to another. (See page 674 in the on-line text book for a
picture…..or do an image search on line.)
18. Igneous rocks are formed by the cooling of molten material as it solidifies
either inside the Earth, or at its surface.
19. Sedimentary rocks are formed over time as sediment is squeezed or cemented
together.
20. Metamorphic rocks are formed when a rock is transformed by heat, pressure
or chemical reactions.
21. Magma could become a Metamorphic rock by cooling into an Igneous rock
and then undergoing heat and pressure to become a metamorphic rock.
V. Relative Dating
22. Scientists use the “Law of Superposition,” which states that sedimentary
rocks form in layers, with the youngest on the top and the oldest on the
bottom. They also use Index Fossils, because if a rock contains an index
fossil the rock must have formed during the time that organism existed on
Earth. (They also use Radioactive Dating, but this really goes along with
Absolute age instead).
23. The “Law of Superposition,” which states that sedimentary rocks form in
layers, with the youngest on the top and the oldest on the bottom.
24. Do not worry about this….Faults, Dikes
25. J, A, H, B, C, X(nothing like THIS part on test), Y, D, I, E, F, G
VI. Absolute Dating
26. Absolute age is determined using Radioactive dating/ Half-Life.
27. A “half-life” is the time required for one half of a sample of a radio-active
isotope to decay. The Half-Life of Carbon-14 is 5730 years.
28. Do not worry about this question….will be covered in Chemisrty
29. I told you to skip this one as wel
30. After EACH half life, half of the sample you start with decays (changes in to
a stable substance). If 4 half lives have gone by, then you have to multiply
½ by itself 4 times OR ½ x ½ x ½ x ½ = 1/16
SOOOOOOO…… you started with 100 grams and end up with 6.25
grams
Start:100g
1 half life later 50 g 2 half lives later 25 g
3 later 12.5g 4 later 6.25g