Chapter 6
P-Waves
(Primary Waves) Arrive at the detector first; They are longitudinal waves which mean the vibrations are along the same direction as the direction of travel
S-Waves
(Secondary Waves) Arrive at the detector of a seismometer second; They are transverse waves which mean the vibrations are at right angles to the direction of travel.
What are the four main processes that shape a terrestrial planet?
1.) Impact Cratering, 2.) Tectonism, 3.) Volcanism 4.) Erosion.
Compare the process of plate tectonics on Mercury, Venus, Earth, and Mars. Why are there varying amounts?
1.) Mercury: No plate tectonics, but geologically newer faults give evidence that Mercury is still contracting. Small size so Mercury is cooling more rapidly than larger terrestrial planets. 2.) Venus: No plate tectonics, but much volcanism. Reason unknown. Perhaps the crust is softer (partially melted) because of Venus's very high temperature. 3.) Earth: Plate tectonics. 4.) Mars: Plate tectonics started, but ceased because Mars's small size allowed it to cool rapidly.
Describe the magnetic fields on Mercury, Venus, Earth, and Mars and state the reasons why they could be like this.
1.) Mercury: Very weak due to slow rotation, but a large iron core 2.) Venus: None due to very slow rotation 3.) Earth: Significant due to a liquid outer core and relative rapid rotation. 4.) Mars: None due to a small core ?
Secondary Crater
A crater formed from the ejected material thrown from an impact crater
Maria (Mare)
A dark region on the Moon composed of basaltic lava flows
Fault
A fracture in a Planet's Crust along which material can slide
Meteor
A meteoroid that enters and burns up in a planetary atmosphere
Lithospheric Plates
A number of relatively brittle segments that compose the Earth's Crust.
What does it mean to say that a planet is differentiated? How do we know this is the case for the Earth?
A planet that is differentiated is one whose layers are ordered by density, with the densest region at the center and the least dense layer at the surface.
Composite Volcano
A volcano formed by thick lava flows alternating with explosively generated rock deposits to build a steep-sided structure
Shield Volcano
A volcano formed by very fluid lava flowing from a single source and spreading out from that source
Which of the following worlds shows evidence of water? Mercury Venus Earth Moon Mars
All of them
Spring Tide
An especially strong tide that occurs near the time of a new or full Moon, when lunar tides and solar tides reinforce each other.
Neap Tide
An especially weak tide that occurs around the time of the first - or third-quarter Moon when the gravitational forces of the Moon and Sun on Earth are at right angles to each other, thus producing the least pronounced tides.
What is an impact crater?
An impact crater is a bowl-shaped depression on the surface of a planet or moon caused by the collision of the planet or moon with meteoroids or asteroids.
Meteorites
Any meteoroid that survive to hit the ground
How does convection play a role in plate tectonics?
Convection currents are set up in the mantle so that the mantle heated room below rises and the mantle near the crust cools and sinks forming convection cells. The motion of the mantle carries the continental plates that float on top of it. The motion of these plates causes mountain ranges, rift valleys, and more.
Magnetic Field
Created by moving charges and exerts a force on magnetically reactive objects, such as iro
Tectonism
Deformation of the lithosphere of a planet
Select all the planets where plate tectonics occur. Mercury Moon Venus Mars Earth
Earth only
What is the relationship between the Sun and the Moon for spring and neap tides?
For spring tides to occur the Earth, Moon, and Sun must be in a line (at New Moon or Full Moon). For neap tides to occur, the Moon must be at right angles to the direction of the Sun (First and Third Quarters).
What is the evidence that water once flowed on Mars?
Gulley channels, water-worn gravel embedded in sand, water ice found below surface by lander, mud flows from craters.
Radioactive Heating
Most of the thermal energy in Earth's interior comes from long-lived radioactive elements trapped in the mantle. As the radioactive elements decay, they release energy, which heats the planet's interior. As radioactive elements decay, the amount of thermal energy generated declines, and Earth's interior becomes cooler as it ages.
What causes magnetic fields?
Moving electrical charges, called an electric current, causes a magnetic field.
Tidal Heating
One source of continued heating is friction from the tidal effects of the Moon and Sun. Tidal effects are caused by the change in strength in gravity across a solid object. Tidal stresses cause the ground to rise under you which takes up a lot of energy that ends up being converted to heat; Contribute around 6% to the heating in the interior
Describe the two types of seismic waves produced by earthquakes.
P-waves travel through both solids and liquids. S-waves travel through solids only.
Cooling
Planets lose thermal energy from their surfaces primarily through radiation. the rate at which a planet cools depends on its size - a larger planet has a larger volume of matter and more thermal energy trapped inside and smaller planets have more surface area in comparison to their small volumes so they cool off faster.
4-1. What is plate tectonics?
Plate tectonics is the theory by which lithospheric plates move over time forming various land forms.
How can the surfaces of the Moon and Mercury undergo weathering when those object have neither running water nor an atmosphere?
Radiation from the Sun will decompose some types of minerals over a long period of time. Impacts of micrometeorites will chip away at the surface rocks. Landslides can occur on hills and mountains.
Meteroids
Small (< 100 m) cometary or asteroid fragments in space
Why do smaller planets and moons cool off faster than larger ones?
Smaller planets and moons cool off faster than larger ones because the surface area to volume ratio is larger for smaller objects than bigger ones. That is, for smaller objects there is more surface area for the heat to escape and a smaller volume of material to "contain" that heat.
Mantle
Solid portion, lying outside of the core, which is made of medium-density materials
Hot Spots
Spots on Earth where hot deep-mantle material rises, releasing thermal energy
What are spring and neap tides?
Spring tides are higher than normal high tides and lower than normal low tides. Spring tides are more extreme than normal tides. Neap tides are lower than normal high tides and higher than normal low tides. Neap tides are less extreme than normal tides.
Describe the Earth's structure.
The Earth's structure from outer to inner: Crust: the lower density, solid layer we live on. Mantle: medium density materials, "soft" enough to flow Outer core: dense materials (iron, nickel), liquid in nature Inner core: dense materials (iron, nickel), solid
Lithosphere
The crust and part of the upper mantle; modified by tectonism
Erosion
The degradation of a planet's surface topography by the mechanical action of wind and/or water.
What is the difference between a meteoroid, meteor, and meteorite?
The difference between a meteoroid, meteor, and a meteorite is where they are found. 1.) A meteoroid is a chunk of interplanetary debris in orbit around the Sun. 2.) A meteor is a small piece of interplanetary debris entering Earth's atmosphere and heating air molecules, which then emit light. 3.) A meteorite is any part of a meteoroid which survived its passage through the atmosphere and has landed on the ground.
What causes tides?
The difference in the gravitational force between the near and far sides of two objects causes tides. (Remember from a previous chapter the force of gravity decreases as the distance between two objects increases.)
How does tidal heating keep the interior of a planet or moon hot?
The friction caused by the materials inside a planet or moon moving past each other as the moon or planet stretches produces heat.
Plate Tectonics
The geographical theory concerning the motions of lithospheric plates, which in turn provides the theoretical basis for continental drift
Lunar Tides
The gravitational pull of the Moon that causes Earth to stretch along a line pointing approximately in the direction of the Moon.
Solar tides
The gravitational pull of the Sun that causes Earth to stretch along a line pointing approximately in the direction to the Sun.
Where do you find the most geologically active places on the Earth? Why?
The most geologically active places on the Earth are found near the plate boundaries for this is where the plates interact with each other.
Differentiation
The process by which materials of higher density sink towards the center of a molten or fluid planetary interior.
Impact Craters
The scar of the impact left on a solid planetary or moon surface by collision with another object
How does the rate of rotation and the size of the planet determine whether or not a planet will have a magnetic field or not?
The size of the planet determines if its interior is molten. The rate of rotation, period of rotation, determines whether the electric currents will be formed in the liquid portion of the core.
Tide
The stretching of the mass of one body due to the gravitational pull of another
Convection
The transport of thermal energy by the movement of packets of gas or liquid
What is the difference between the volcanoes found on Earth and those found on Venus and Mars?
The volcanoes on Mars and Venus are shield volcanoes, which are wide, low-profile volcanic cones produced by highly liquid lava. The volcanoes on Earth are mostly composite volcanoes, which have steep sides formed by successive lava and ash flows. Some shield volcanoes are also found on Earth, for example, the Mauna Loa in Hawaii.
Why are there so many craters on Mercury and the Moon?
There are many craters on Mercury and the Moon because neither body has an atmosphere to vaporize the meteoroid before it reaches the body's surface.
Why are there so few craters on Venus and the Earth?
There are so few craters on the Earth because most have been destroyed due to plate tectonics and erosion. There are so few craters on Venus because lava flows have filled in the craters. Also, both planets have atmospheres, which cause the smaller meteoroids to vaporize or broken up into smaller pieces.
Crust
Thin, hard layer, covering the mantle, made of lower-density materials that is chemically distinct from the interior
Which planets have the most volcanisms and which ones the least. Why?
Venus: has the most volcanism with hundreds of volcanic features. May still be occurring today. Earth: is next with its many active volcanoes. Mars: has the largest volcano in the Solar System, which grew as it remained over a hot spot. Mercury: has some volcanic features, but not many.
Where is that water now?
Water ice exists in a layer beneath the surface, at the poles, and small amounts of ice crystals mixed in the soil.
Seismic Waves
Waves produced by Earthquakes
What is radioactive heating and how does it keep the core warm?
When a radioactive material decays it gives off energy. This energy heats the interior of a planet.
What are the processes of weathering on Venus, Earth, and Mars?
Wind erosion: occurs on Venus, Earth, and Mars. Water erosion: only on Earth.
Neap tides occur when the Moon is in the third or first quarter phase. This results in a.) smaller than usual tides. b.) larger than usual tides. c.) no tides.
a.) smaller than usual tides.
Spring tides occur only when a.) the Moon is in the new or full phase. b.) the Moon is in the waning or waxing gibbous phase. c.) the Sun is near the vernal equinox in the sky. d.) the Moon is in the first or third quarter phase.
a.) the Moon is in the new or full phase.
What are the sources of heat in the interior of a planet? a.) Solar energy. b.) Radioactivity. c.) Heat that was generated when the planet formed. d.) Tidal heating.
b.) Radioactivity. c.) Heat that was generated when the planet formed. d.) Tidal heating.
Scientists learn about the interior structure of the Earth by using a.) observations of magnetic fields. b.) observations of seismic waves. c.) X-ray observations from satellites. d.) ground-penetrating radar. e.) deep mine shafts.
b.) observations of seismic waves.
A planet in which volcanism is highly active would likely a.) have a high number of visible impact craters. b.) have no atmosphere. c.) have relatively few craters on its surface. d.) have a completely smooth surface.
c.) have relatively few craters on its surface.
Earth has fewer craters than Venus? Why? a.) Earth's atmosphere provides better protection than Venus's. b.) Earth is a smaller target than Venus. c.) Earth is closer to the asteroid belt. d.) Earth's surface experiences more erosion and plate tectonics than Venus.
d.) Earth's surface experiences more erosion and plate tectonics than Venus.
Erosion is most efficient on planets that have a.) plate tectonics. b.) volcanoes. c.) bombardment by meteoroids. d.) an atmosphere and liquid water
d.) an atmosphere and liquid water
Earth's innermost core is solid, not liquid, because a.) differentiation caused all of the heavy, solid material to sink to the bottom while Earth was forming. b.) all the liquid has moved up into the mantle via convection. c.) the core temperature is too low to melt iron. d.) the pressure is too high for a liquid state.
d.) the pressure is too high for a liquid state.
Lava flows on the Moon and Mercury created large, smooth plains on those worlds. We don't see similar features on the Earth because a.) Earth had fewer large impacts than those worlds did. b.) Earth had less lava than those worlds. c.) Earth is larger than those worlds, so the plains are not as noticeable. d.) Earth's rotation rate is much faster than that of either the Moon or Mercury. e.) Earth has plate tectonics that change its surface.
e.) Earth has plate tectonics that change its surface.
Core
the innermost region of Earth's interior (consists of 2 components)