Download Unit 2 Study Notes

8th Grade – Earth Science
Unit 2 Study Notes
1. Minerals are composed of elements, rocks are made of minerals.
2. When using a streak test, a geologist determines the color of the powder of a mineral.
3. Sea-floor spreading occurs as oceanic plates are diverging from one another. Magma rises along
a rift zone and spreads out at the surface, building new ocean floor.
4. At one time all continents were joined together to form one large landmass called Pangaea.
South America and Africa show the most evidence of having been joined at one time.
5. As Earth’s plates move apart at some boundaries, they collide at others forming mountains and
volcanoes.
6. The Himalayan Mountains are still forming today due to the Indo-Australian Plate and the
Eurasian Plate colliding and pushing up the crust.
7. Of the four main layers of Earth, the inner core is the most dense, and the crust is the least
dense.
8. The Earth’s plates are moving because of convection currents in the mantle.
9. The three main interactions between plates are: spreading apart (divergent plate boundaries),
moving together (convergent plate boundaries), and moving past each other (transform plate
boundaries).
10. Sedimentary rocks form when smaller pieces of sediment go through the processes of
compaction and cementation.
11. Vibrations that move through the ground carrying the energy released during an earthquake are
called seismic waves.
12. According to the theory of plate tectonics, Earth’s plates move very slowly in various directions.
13. When you touch a hot plate, the transfer of heat from the plate to your hand is called
conduction.
14. Scientists think that the outer core, made of liquid iron and nickel, moves to produce Earth’s
magnetic field.
15. The energy from the sun that warms your face is transferred by a process called radiation.
16. A series of processes known as the rock cycle slowly changes rocks from one kind to another
kind.
17. The hypothesis of continental drift was that all the continents once were joined as a single
supercontinent and have since drifted apart.
18. The ocean floor sinks beneath a deep-ocean trench and back into the mantle in a process known
as subduction.
19. A major volcanic belt known as the Ring of Fire circles the Pacific Ocean.
20. Molten material that leaves a volcano’s vent is called lava.
21. The upper layer of Earth is broken into more than a dozen plates that move very slowly in
various directions.
22. Mantle material rises in convection currents because heated materials become less dense.
23. Pressure increases from Earth’s surface toward the center of Earth.
24. Oceanic crust near the mid-ocean ridge is younger than oceanic crust farther away from the
ridge.
25. An active volcano is erupting or may erupt in the near future.