Chapter 12: The Dynamic Planet (rock cycles, tectonics) Flashcards
Define endogenic vs. exogenic systems.
- Endogenic - internal process that produces flows of heat and material from deep below earth’s crust (ex. tectonics, earthquakes, volcanism)
- Exogenic - external processes operating at earth’s surface; the movement of air water, ice which are all powered by solar energy (ex. rivers, landforms, erosion, weathering, glaciers, oceans)
Provide examples of short and long timescale events.
-Long time-scale events are like mountain formation, canyon incision, formation of breaking up of supercontinents (plate tectonics)
-Short time-scale events - volcanic eruptions, meteor impacts, and landslides
Describe the geologic time scale: How are boundaries between eras and periods determined? Which encompasses a bigger amount of time, an era, eon, period, or epoch?
The geological time scale is subdivides the 4.6 billion years into eras, eons, period and epoch going from largest to smallest.
- The boundaries between each interval is mostly based on major events in earth’s history
-Eon is the largest, then an era, then period, then epoch, which is the smallest amount of time.
Name and describe Steno’s principles of stratigraphy.
1.) Principle of superposition - rock and sediments are organized where the ones at the bottom are the oldest, and the ones on top are younger
2.) Principle of original horizontality - Rock layers are originally deposited as flat, horizontal layers under action of gravity (only true for sedimentary rock or volcanic flows)
- if tilted, folded, or deformed, it must have occurred after
3.) Principle of lateral continuity - sediment layer extend laterally (sideways) at first in all directions until thinned to zero or stopped at barrier (due maybe to erosion)
4.) Principle of cross-cutting relationships - geologic feature that cuts another is younger of the two features
How old is the universe? The Earth? How do we know? What age are some of the oldest rocks on earth and where are they found?
-The solar system (universe) and sun are estimated to have occurred more than 4.6 billion yrs ago
- The Earth is about 4.6 billion yrs old
-We know about Earth’s age because of the oldest rocks and fossils, which are about 4 billion yrs old
-also by absolute ages, absolute dating, radiometric dating
- The Acasta Gneiss is the oldest rock on earth, found in The Northwest Territories; age is about 4.3 billion yrs old
What is absolute dating? How is it different from relative dating?
- Absolute dating provides exact numerical ages of materials through ways like annual layer counting (ex. tree rings, lake layers, glacial ice layers)
-Relative dating informs on how old something is in relation to other objects, but can’t provide a specific exact age
Define the term “Uniformitarianism”.
It’s the principle that physical processes in today’s environment have been operating throughout geological time.
-Understanding present processes is key to understanding the past
How, in basic terms, is the Earth thought to have formed?
It was thought to have condensed and congealed from nebula of dust, gas, and icy comets
Describe (materials, state or matter, depth) the layers of Earth’s interior.
How do we know this info?
-Core in general - inner part of the Earth (2,900 km below surface). It’s a dense ball made up 90% iron and 10% nickel, oxygen, & sulfur
-Inner core - Solid; about 1,200 km thick
-outer core - liquid; about 2,260 km thick
- Mantle - mostly made by peridotite; layer of earth beneath crust; near the bottom, temp is 4000 degrees Cel., near top is 850 degrees. (rigid is part of lithosphere); even though its solid rock, it can slowly flow due to high temp and pressure
- Scientists use seismic waves created by earthquakes to probe earth internal structures
- it send shock waves throughout planet
-Liquid zones absorb seismic waves
-Density changes induce reflections and refraction of seismic waves
What is the cause of earth’s magnetic field? What function does it serve?
-The fluid outer core generates 90% of Earth’s magnetic field, because it’s made of liquid molten metallic iron
- It protects our planet from cosmic radiation and from the charged particles emitted by the sun
- Provides basis of navigation with a compass
Compare and contrast continental and oceanic crust (composition, density, thickness)
-Continental crust - the land we see; thicker of the 2 due the mountains and valleys
- mostly granite (crystalline)
- low density (2700-2800 kg/m3)
- mostly silicon (aluminum, potassium, sodium, calcium)
- Oceanic crust - ocean floor
-thinner crust but denser due to denser materials
- more basalt
- high density (3000 kg/m3)
- mostly silicon, magnesium, iron
Define isostacy and provide examples of situation that result in isostatic depression and rebound.
-Isostacy - a state of equilibrium between
the lithosphere and atmosphere
- Ex. Greenland was experiencing isostatic depression due the crust sinking into the asthenosphere by the Greenland ice sheet. However due to deglaciation induced by climate change, the regions near sinking ice sheet have begun to uplift and rebound.
Define the term mineral and explain why silicates are the most common mineral group.
- A mineral is an inorganic (non-living) natural solid that has a specific chemical formula and usually has a crystalline structure w/ physical properties that allows us distinguish.
- Silicates is the most common group because it makes of about 95% of the earth’s crust; since there’s so much of silicon and oxygen on Earth, they have a readiness to combine w/ each other and other elements
Define the term, rock.
-A rock is an assemblage of minerals bound together
-Could also be a mass of a single mineral (rock salt), or undifferentiated material, or even solid organic material (like coal).
Explain how igneous rocks form and what causes them to be fine grained vs. coarse.
- Igneous rocks solidify (crystallize) from molten state; they form from magma (molten rock beneath earth’s surface)
- When plates collide, denser plate goes underneath less dense plate
-Water goes down w/ it as well and into the crust and the water starts to evaporate as temp rises and melts continental rocks, turning it into magma - magma rises from mantle toward crust; cools down once it reaches ocean; becomes oceanic crust.
- The location and rate of cooling is what determines texture of rock
-slower cooling of magma below surface allows time for crystal formation, resulting in coarse-grained rocks (granite)
-Intrusive igneous rocks - faster cooling magma at the surface results in finer-grained rocks (basalt)
-Extrusive igneous rocks
