First Geology Quiz - Ch. 10, 9 and 4
What characteristics increase as we descend towards Earth's center?
density, pressure and temperature
Define tephra
rock fragments and particles ejected by a volcanic eruption.
transform plates are...
sliding past eachother
What is permanentism?
The false belief that continents and oceans have always been generally as they are today.
What is pyroclastic debris?
volcanic material formed during an explosive eruption
Is the lithosphere solid or liquid?
3solid
What are the six types of volcanoes?
Cinder cone, composite volcano, shield volcano, large igneous provinces, sea-floor volcanism, and kimberlite
Who coined the term "Pangea" and what does this term mean?
- Alfred Wagner - Means "all land" in Latin - Believed that the continents were joined together during the Permian
Name some of the things Wagner did to support his theory.
- Sedimentary strata in South America matching those in Africa. - North American coalfields matching those in Europe. - Mountains of Atlantic Canada matching those in northern Britain.
Plate tectonics is the model or theory that explains...
- the origins of continents and oceans - origins of folded rocks and mountain ranges - igneous and metamorphic rocks - mountain ranges - earthquakes - volcanoes - continental drift*
Why wasn't the theory of plate tectonics not accepted until 50 years ago?
- was difficult for established geologists to accept - political gulf between Alfred Wagner (German) and those he was trying to convince (USA/Britain) - did not have evidence to support theory until the 20th century
What are the six most important signs that a volcanic eruption is likely to occur soon?
1.) Gas leaks 2.) Bit of a bulge 3.) Getting shaky 4.) Dropping fast 5.) Big bump 6.) Blowing off steam
How much do continents drift from each other in a year?
2.5 centimeters
What is a geosyncline?
A thick deposit of sediments and sedimentary rocks, typically situated along the edge of a continent.
Where does most of Earth's volcanism take place?
Along the spreading ridges on the sea floor.
Define a subaerial eruption
An eruption that occurs on land
Magma is formed at three main plate-tectonic settings. They are...
Divergent boundaries, convergent boundaries and mantle plumes
What are some differences between mafic and felsic magma?
Felsic magmas tend to be more viscous because they have more silica. Felsic magma also has a higher level of volatiles, that is, components that behave as gases during volcanic eruptions.
What peaked Alfred Wagner's interest in the theory of plate tectonics early on?
In the newspaper, he read about matching Permian-aged terrestrial fossils in different parts of South America, Africa, India, Antartica and Australia.
What did the probe that Edward Bullard create show?
It measured the flow of heat from the ocean floor. The rate was higher than average along the ridges and lower than average in the trench areas. Showed there was convection in the mantle. the areas of high heat flow being correlated with upward convection of hot mantle material, and the areas of low heat flow being correlated with downward convection.
Which of Earth's layers break into pieces we call plates?
Lithosphere
What does mafic and felsic mean?
Mafic is dark colored minerals (think of dark magic) like olivine. Felsic is light colored minerals like feldspar.
Which is denser - mantle rock or crustal rock?
Mantle rock
The boundary between the crust and the mantle is known as the...
Mohorovičić (or Moho) discontinuity
Which of Earth's layers is liquid?
Outer core
When rocks are sampled from the same place at different times, are their magnetic pole positions different or the same? Why or why not?
Rocks that are sampled from the same location but at different times have different magnetic pole positions. The magnetic data defines movement with continents. The magnetite in rocks will orient themselves depending on where the continent was at the time of the creation of the rock.
Is the upper and lower mantle solid or liquid?
Solid but plastic
Explain remnant magnetism
The direction and force of Earth's magnetic field changes over time, largely believed to be caused by convection currents. Any mineral containing magnetite will become magnetized with an orientation parallel to that of Earth's magnetic field at that time.
What is istostasy?
The literal definition is standstill. However this theory is important to geology because it defines the principle that earth's crust is floating on the mantle.
What was the prevailing theory on the origin of mountains by the end of the 19th century?
The prevailing theory was contractionism. This theory believed that since the Earth is slowly cooling, it must also be slowly shrinking. Mountains would form like wrinkles on an apple. This theory was proven wrong as the amount of cooling could not cause the necessary amount of shrinking.
What are composite volcanoes associated with? Give an example of a composite volcano.
They are associated with subduction at convergent plate boundaries. In many of these volcanos, magma is stored in a magma chamber in the upper part of the crust. An example of one would be Mount St. Helens in Washington.
Where aare most divergent boundaries located?
They are usually located on mid-ocean ridges
Do composite volcanoes form quickly or slowly? Do they last for a long time?
They form quickly and last for a short amount of time
What did Wagner propose to be the cause of continental drift by the end of his life?
Wagner believed that the continents were floating like icebergs on the heavier SIMA crust. The only forces that Wagner thought could propel the continents were poleflucht. Poleflucht is the effect of Earth's rotation pushing objects toward the west. It was quickly proven that these forces were too weak to move continents.
What is Aa lava?
a lava flow that solidifies with a blocky surface
What is a shield volcano? Give an example
a low-profile volcano formed primarily from eruptions of low-viscosity mafic magma. Mount Mauna Loa in Hawaii
Define lahars.
a mudflow or debris flow that is caused by a volcanic eruption.
What are pillows?
a pillow-shaped mass of volcanic rock (typically basalt) formed when magma erupts beneath the surface
Define mantle plume or hot spot
a place where hot mantle material rises in a stationary and semi-permanent plume, and affects the overlying crust
define lava levees
a ridge that forms along the edge of a lava flow because the magma at the edge cools faster than that in the middle.
What is a compression wave?
a seismic body wave that shakes the ground back and forth in the same direction and the opposite direction as the direction the wave is moving.
What are body waves?
a seismic wave that moves through the interior of the earth
Define transform faults. Give an example
a type of fault in which two tectonic plates slide past one another. San Andreas fault
Define caldera
a volcanic depression that is many times larger than the volcanic vents within it.
Define a subaqueous eruption
a volcanic eruption that takes place under water.
What is a mantle plume?
an ascending column of hot rock (not magma) that originates deep in the mantle, possibly just above the core mantle boundary.
Define volcano
any location where magma has come to the surface, or has done so within the past several million years.
What are cinder cone volcanos mostly made up of? Give an example of a cinder cone volcano
fragments of vesicular mafic rock. The Eve Cone in northern B.C.
What is isostacy?
gravitational equilibrium between the lithosphere and asthenosphere. (Lithosphere sinks into asthenosphere)
The core is primarily composed of...
iron
define pahoehoe
lave cooled rapidly and forms at the surface, looks like a ropy texture.
Name the main three layers of Earth
mantle, crust, and core
Divergent plates are...
moving apart
convergent plates are...
moving together
What can we learn by studying both the horizontal and vertical components of the remnant magnetism?
one can tell not only the direction to magnetic north at the time of the rock's formation, but also the latitude where the rock formed relative to magnetic north.
Is the asthenosphere solid or liquid?
partially liquid
Which of Earth's layers is the thinnest?
the crust
What is columnar jointing?
the fracturing of rock or sediment (but typically volcanic rock) into columns that are typically six sided.
define paleomagnetic dating
the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials
What is seismology?
the study of vibrations within earth
Name one example of where a hot spot is
yellow stone