Chapter 4
What proposed ideas came before the plate tectonics theory?
Contracting Earth Hypothesis: Earth was a molten ball that cooled and cracked on the surface, creating mountains and collapses for oceans.
Continental Drift Hypothesis: Continents occupied different locations on Earth's surface in the Geologic past. Theory proposed by Alfred Wegener.
What is the recurrence interval?
The time between events is called the recurrence interval. The stress along the fault takes time to build up and eventually triggers an earthquake.
What is the volcanic explosivity index (VEI)?
The Volcanic Explosivity Index (VEI) measures volumes of erupted material.
Name and compare each rock type.
Igneous: Form from cooling lava.
Sedimentary: Form from mineral or rock fragments, crystalize from a solution, or form through biochemical processes.
Metamorphic: Form when pre-existing rocks are altered by heat and pressure.
What does the theory of plate tectonics state?
The Earth's outermost layer is fragmented into about a dozen large and small plates moving relative to one another above hotter, more "fluid" material (Outer Core).
What are the differences between a normal, reverse, and strike-slip fault?
Normal Fault: Road block above the fault plane moves down.
Reverse Fault: Road block above the fault moves up.
Strike-Slip Fault: Blocks on either side of fault move horizontally, left or right.
Name the types of Volcanic Mountains.
- Shield Volcano: Broad, gentle slopes. Built from many low viscosity lava flows. Relatively mild eruptions associated with hot spots, divergent plate boundaries.
- Stratovolcanoes: Most common. Steeper slopes built from alternating layers of tephra and medium viscosity lava. Form on plates overriding subduction zones at convergent plate boundaries.
- Cinder Cone Volcanoes: Smallest. Built from more viscous magma. May form on slopes of shield or stratovolcanoes.
What classifies a mineral?
- Naturally occurring
- Inorganic
- Solid
- Definite chemical composition
- Orderly internal arrangement of atoms
Name the Earth's layers.
1.) Crust: Low-density rock made of oxygen and silicon.
2.) Mantle: Solid, consists of oxygen, silicon, and magnesium. The rocks at the top are closer to the melting point.
3.) Core: Inner core is solid. The outer core is partially melted iron and nickel.
Name and define the different earthquake features.
Faults: Fractures where two massive sections of rick most past each other. Zone of weakness where earthquakes occur.
Fault Plane: Boundary between rocks
Focus: Locations where movement begins on fault
Epicenter: Location on surface above the focus
Fault Scarp: "Steps" in land surface formed by movement on the fault
What are the volcanic features without lava according to their definition?
Geysers: Water heated under pressure with volcanic gases.
Hot Springs: Heated groundwater rises to surface.
Mud Volcanoes: Chemical reactions convert rock to soupy clay.
What are the differences in mineral cleavage, crystal form, and hardness?
Mineral Cleavage: Minerals breaking along planes of weakness defined by atomic structure.
Crystal Form: The arrangement of the faces of a crystal to form a particular shape.
Hardness: The resistance of a mineral to scratching. Ranked using the Mohs Hardness Scale.
Double points if both questions answered: What is the lithosphere? What is the Asthenosphere?
The lithosphere is a rigid layer composed of the crust and the uppermost mantle. It is broken into the pieces we call tectonic plates.
The asthenosphere lies directly under the lithosphere, made of melted and cooled bits of the mantle.
Describe the specified purposes of the Moment, Richter, and Mercalli scales.
Moment Magnitude Scale: Measures the total energy released by an earthquake.
Richter Magnitude Scale: Determined from the seismograph's data. Where the largest amplitude is used to determine the magnitude. Essentially, it measures the amount of shaking.
Mercalli Intensity Scale: Earthquake described in terms of people's experience as well as the damage done to nearby structures.
Name the magmas with high/low viscosity, and which ones result in mild and explosive eruptions.
Basalt has low viscosity. Andesite has intermediate viscosity. Rhyolite has the highest viscosity. Higher viscosity = More violent eruptions
What is liquefaction?
Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking.
Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes.
Name and describe the key seafloor features.
Continental Shelf: A narrow extension of the continent that is submerged underwater.
Abyssal Plain: Level seafloor that makes up the deep ocean; contains underwater seamounts and volcanoes.
Oceanic Ridge: Submarine mountain ranges that contain most of the world's Volcanic Activity. (found toward center of oceans)
Oceanic Trench: Narrow, deep portions of the ocean floor. (most common around the Pacific Ocean)
Compare S-waves, P-waves, Rayleigh Waves, and Love waves.
Body Waves -
P-waves: Primary waves have the fastest seismic waves (4-6 km/s in crust). First to be detected. Travel like a slinky.
S-waves: Secondary waves travel roughly 3-4 km/s. Waves travel like rope.
Surface Waves-
Rayleigh Waves: Cause the surface to rise and fall like ocean waves. (slowest overall)
Love Waves: Produce surface shearing, which causes side to side movement.
What were the signs of Mount St. Helen's eventual eruption?
- Increasing frequency of earthquakes. 44 earthquakes in the 5 years leading up to the eruption.
- Followed by change in shape of cone. 2km diameter bulge on North Flank.
- Release of volcanic gases: steam, sulfur dioxide, carbon dioxide, and hydrogen sulfide.
What are minerals made of?
Minerals are made of elements.