Chapter 10 Flashcards
What may cause motion in the crust floating on top of the liquid layer of a planet?
Convection generated by internal heating
What determines the amount of geological activity a planet produces?
The size of the planet is the determining factor
What determines the amount of heat inside each planet?
It is a function of mass (approx r^3)
What determines the amount of heat lost by a planet?
The internal temperature and the surface area of the planet
What event is caused by tectonic plates “sticking” and then suddenly “slipping”?
An earthquake
What is a volcanic hotspot?
An area in which molten lave rises up through a hole in the tectonic plate or at a plate boundary
As plate tectonics move towards each other and uplift, what geological feature forms?
Mountain ranges
When plate tectonics move away from each other, what geological feature forms?
Volcanoes (and hotspots)
What does the Richter scale measure?
The energy released by an earthquake (not the damage produced)
How much more energy is there is an earthquake one degree higher on the Richter scale?
10x more
What Earthen feature allowed the continents to break apart?
The lubrication from the water
How do we know that the magneitc north pole of Earth changes location?
From the alternating polarity patter we observe in the Mid-Atlantic Ridge
What evidence do we have for tectonic activity on Mars?
The Acheron Fossae region shows rifting across older impact craters with at least 3 alternating horsts and grabens
The process in which material is brought from the interior of the planet to the surface is called what?
Volcanism
Where can one expect to find shield volcanoes?
Above hot spot regions of the mantle where hot material rises
How are shield volcanoes formed?
Lava erupts repeatedly from a fluid magma chamber and builds up on the surface
How are volcano chains formed?
Tectonic plates moving over a hotspot produce a line of volcanoes
What are the two types of lava flows?
Pahoehoe (smooth) and A’a’ (jumbled)
Where is a wrinkle ridge usually found?
In mare lava plains
How are wrinkle ridges formed?
From tectonic stresses associated with the cooling and contracting of lava that flooded a mare lava plain
What is the difference between a sinuous rill and a linear rill?
Sinuous: winding valley (resembles a channel cut by a river or lava flow), linear: straight sided (like a graben)
Wind carrying small particles, which bounce on the surface and dislodge larger particles, is called what?
Saltation
Why is it that some regions of Mars look similar to an Earthen desert?
This id due to the wind erosion on Mars which is similar to that of Earth
How is dust deposited on the upwind side of Martian craters?
By wind streaks across the Martian plane
What is a geologic cycle?
On planets with atmospheres, the surface may be transformed in even more ways (ex. the rock cycle)
What is the name of the reaction that is the geothermal link between rocks and the atmosphere and what does it do?
The Urey Reaction (volcanic gas dissolves in rainwater/oceans, forms weak carbonic bonds which can form rocks)
What drives the unusual chemical reactions on Venus?
Its thick atmosphere
The red soil on Mars is due to what?
The oxidization of iron atoms in the minerals (same process as that on Earth)
The study of the evolution and configuration of landforms is called
Morphology
What evidence to we have of global shrinkage on Mercury?
Surface ridges indicate some degree of planetary cooling
“The zone in the early SS in which Mercury formed was unusually rich in Fe” is which formation theory for Mercury?
Selective accretion
“Intense solar heating drove off most silicates after Mercury formed” is which formation theory for Mercury?
Postaccretion vaporization
“Single large impactor collided with fully formed and differentiated Mercury and explosively removes most of the outer silicate crust” is which formation theory for Mercury?
Giant Impact hypothesis
What is the primary mineral found in the lunar highlands?
Anorthosite (related to feldspars)
Deep craters in the highlands imply what about the anothosite layer?
That is layer must be at least tens of km deep
What does the large amount of anorthosite on the lunar surface imply about past events?
That a large fraction of the moon was once entirely melted (perhaps during its formation in a grazing impact with the Earth) to allow the anorthosite to float up
Why are the lunar mare dark in colour?
The large presence of basalt
The lave outflows were to result of which two possible
Either large impacts several hundred Myr after lunar formation or a buildup of delayed localized heating by radioactive decay
Explain the lunar formation “fission theory”
The breaking up of early, rapidly rotating Earth or initially double-planet (pro - the earth’s outer layers and moon have similar densities, con - the earth and moon have fairly different compositions, con - the earth-moon system has too little L to support theory)
Explain the lunar formation “Capture Theory”
Moon formed elsewhere and is somehow captured by the Earth (con - capture is very difficult, con - the moon’s composition is not consistent with the formation anywhere is in the SS)
Explain the lunar formation “Co-Accretion Theory”
Both bodies formed in the same disk of material (con - they are fairly chemically different, con - too much L in the moon for this theory)
Explain the (best) lunar formation theory “Impact hypothesis”
One large Mars-sized body grazed Earth and subsequent mixed material went into orbit about a proto-Earth to form the moon (pro - explains the chemical differences between earth and moon, pro - explains lack of volatiles in the moon and small amount of Fe)
What geological feature dominates the surface of Venus?
Vast “mare”-like lava plains
Do we have any evidence for ongoing volcanic activity on Venus?
We have no unambiguous direct evidence
Is there tectonic activity on Venus?
Yes, but not to the same degree as we see on Earth (no plate subduction or movement evident)
What is the age of Venus’ surface?
300-750 Myrs (much younger than the other terrestrial worlds, and closer to Earth)
What are the three main theories for the young age of the surface of Venus?
- Resurfacing from lava flows, 2. plate tectonics are active, 3. Catastrophic Mantle Break up
Which region of Mars has the highest impact crater density?
The southern “highlands”
What is the only type of volcano found on Mars?
Shield volcanoes
What evidence has been gathered to prove extensional tectonics on Mars?
The way the Martian crust is rifted (“split”) on broad regional scales
What are the two large volcanic provinces on the Martian surface?
Tharsis (containing Olympus Mons) and Elysium
What did the two moons of Mars (Demios and Phobos) start their life as?
Most likely as asteroids, later captured by Mars
What are 4 large scale Martian surface features that suggest water was once present?
River like valley networks, outflow channels, waterflow features (ex. teardrop islands), and splash craters
What feature, found on Mars, suggests a more recent presence of water?
Gullies (originally thought of as seepage of ground water, now through to have formed by snow and ice melting)
What was found in evaporite beds on Mars
Salts and hydrated minerals
What does the presence of hematite “blueberries” on Mars indicate?
These form in the presence of water on Earth, therefore, mars probably had at least a few salty water bodies that have evaporated
