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Geology Test 2
Terms in this set (59)
Volcanoes are associated with?
convergent plate boundaries and hot spots
Magic Eruptions are
Effusive (abundant low viscosity lava)
very large but not steep or high, frequent but nonexplosive eruptions with lava flows.
shield volcano example
Mauna Loa, Hawaii, Iceland
lava erupts from a crack and "floods" a flat area
Fissure eruptions example
Columbia River Valley, Rift Valley of Africa
small volcanic cones made of scoria or vesicular basalt usually with a crater. Lava flows may erupt from the base. These are very common in the western USA and make a frequent appearance in movies filmed around Hollywood. They tend to erode easily.
the crust of a small lava flows hardens, leaving the lava to flow through a small tunnel which may be left filled with air after the lava source is gone.
Polygonal cracks which develop as hot lava (or a hot pyroclastic flow) cools and shrinks. Ex: "Devil's Tower", Wyoming, and "Devil's Postpile", California.
fluid lava that develops rope-like wrinkles on the surface
stickier lava that is cindery and blocky
lava that erupts into cold water develops pillow-shaped blobs because the outer surface cools rapidly.
Intermediate / Felsic Eruptions
Explosive, high viscosity lava, occur near convergent plate boundaries
Stratovolcanoes or composite cones
large, high volcanoes with concave sides made of layers of ash and lava flows. Ex: Vesuvius, Mt. St. Helens, Yellowstone, Krakautoa. Eruptions are infrequent, but extremely explosive. Yellowstone has erupted at least three times in geologic history. If it goes off again it would be catastrophic (but thankfully it is showing no signs of waking up soon).
large collapse of the top of the volcano after the magma chamber blows and everything settles down. Ex: Crater Lake, Oregon
Very hot ash (tephra) which entrains air, then flows very rapidly downslope like an avalanche. Ash is made of tiny shards of volcanic glass. Very deadly, kills instantly. Ex: Pompei
Large amounts of ash ejected from a big explosion can hang around in the earth's atmosphere for several years, causing cold weather because it blocks sunlight. It's bad for airplanes too!
mixture of ash and water (typically from rapidly melted snow or glaciers) makes a mudflow which can travel like wet concrete down river valleys. Not fun. Ex: Armero, Columbia was buried under 16 feet of mud and debris, killing over 23,000 people.
Sometimes a lake within a volcanic crater can "burp" carbon dioxide. This deadly cloud travels quickly downslope, suffocating everything in its path. Ex: Lake Nyos, Camaroon
Geysers and fumaroles
Ground water gets heated up by a nearby magma chamber and makes tourists come to Yellowstone. Fumaroles are gas emissions. Not generally dangerous unless you breathe them!
Volcanic Eruptions can be predicted
-earthquake activity increases
-the ground gets hotter
-magma makes the ground bulge upward
-gas and steam emissions increase
There are volcanoes on other planets
-Mars, Olympus Mons is a shield volcano
-Moon, "Maria" or "seas" (dark round places) are made of basalt, and were probably formed when meteorites punched through the thin crust and allowed molten material to escape
Which of these is a NOT associated with a mafic type eruption?
Which of these is most likely to kill people during a volcanic eruption?
In general, which of these types of magma is more likely to cause a dangerously explosive eruption?
A dangerous mudflow caused by a nearby volcanic eruption
Common small scale mafic eruption with scoria
weathering and erosion
how a rock becomes a sediment
rocks get broken into pieces or class (grains)
· JOINTING: EX. EXFOLIATION
· FROST WEDGING
· PLANT ROOT WEDGING
· SALT WEDGING
TALUS SLOPE: DEBRIS PILE FROM WEDGING (USUALLY FROST)
· THERMAL SHATTERING FROM FOREST FIRES
Minerals in rocks are chemically changed to other minerals
Chemical weathering attacks corners and edges
It looks like a rock, but you can dig it with a shovel (feldspars have rotted to clay)
affects mainly rocks made of calcite =limestones
minerals react to water, changed into other minerals. Feldspar to clay
rusting of magic minerals
Minerals absorb water and expand
Common Products of Weathering
· MINERAL GRAINS (USUALLY QUARTZ)- SAND, SILT, PEBBLES
· IRON OXIDES (RED, ORANGE, OR BROWN COLORS IN ROCKS)
· CLAY MINERALS- TINY FLAKES WITH PERFECT CLEAVAGE IN ONE DIRECTION
· IONS IN SOLUTION- SALT, CALCITE, GYPSUM
· ORGANIC MATERIAL- BLACK COLOR IN ROCKS
Differential Weathering of Rocks
- Affects gravestones
- Explains why mountains erode the way they do, forming long ridges and valleys in the folded Appalachians
-composed of weathered rock or sediment
Type and Thickness of soils depend on...
- type of bedrock
- slope steepness
In warm humid climates, limestone is particularly susceptible to which of these weathering processes?
Blocks fall off a cliff due to wedging by frost. At the bottom of the cliff one could expect to find a(n)
In South Carolina it is common to find soils called saprolites that have foliation and mineral veins like metamorphic rocks, but they are soft and can be easily shoveled up. This kind of soil is the result of
Which of these is NOT usually the result of weathering?
Table Rock SC, and Stone Mountain GA are good examples examples of
Sedimentary rocks give us...
evidence for past depositional environments which help us understand the geological history of an area
Sedimentary rocks contain..
-oil and gas
-fossils, clues to the history of life
-important reservoirs of ground water
-caves, which are fun to explore
Clastic sedimentary rocks
Made of grains; pebbles, sand, silt, clay
pebbles, sand, silt, clay when lithified turn to...
Sorting and rounding of grains are
clues to the transportation distance and process
What are special cases of sandstone?
Arkose and Graywacke
Chemical Sedimentary Rocks
precipitated from solution: evaporites (salt and gypsum) and travertine
Organic sedimentary rocks
made of organic debris: Coal
Biochemical sedimentary rocks
both chemical and biological in origin- limestone, dolostone, and chert
can have many textures, is always made of calcite, and always forms in Tropical shallow marine eviroments
is limestone that has been chemically altered by ground water, has more magnesium
(Flint, Agate, Jasper, Petrified Wood) has various origins, but is always made of quarts. Geodes, Arrowheads
Phosphate beds and nodules
occur on the sea floor and replace bone material in the sedimentary rocks around Summerville: Mastodons, horses, shark teeth, and many others.
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