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why rocks?
most earth processes involve rocks, they give us clues about earth's past environment
what is a rock?
a rock is a solid mass of minerals or mineral type minerals
what rock has organic mineral in it?
coal
how many types of rocks are there?
three
Igneous
formed from cooled lava or magma (melted rock)
sedimentary
when rocks are exposed to weathering forces it creates sediments, when those sediments are compacted it creates sedimentary rocks (lithification)
metamorphic
when rocks are exposed to heat (not enough to melt) and pressure, it changed the chemistry of the rock, and it becomes metamorphic
the rock cycle
summarizes how each of these rock types form or is transformed into the other; one type of rock can turn into any other type, it's an unending process
igneous rocks
formed from rocks that have melted and then cooled, some igneous rock formed at the surface but most is underground
what are igneous rocks also called?
volcanic rock
intrusive rock
forms when magma has cooled below the (INside the earth), has larger crystals because of slow cooling
what is intrusive rock sometimes called?
plutonic rock
extrusive rock
forms from lava that cools at the surface (EXited the earth), has smaller or no crystals because of fast cooling
what do we classify rocks based on?
texture and composition
what are the four textures?
phaneritic, aphanitic, porphyritic, and glassy
phaneritic
(coarse grained), preacher cookie, large, easy to see crystals or grains. more are intrusive and cool slowly. ex: granite
aphanitic
(fine grained), sugar cookie, smaller crystals or grains that cool quickly usually at or near surface. ex: basalt
porphyritic
choc chunk cookie, has both large and small crystals because it cools at different times, ex: andesite porphry
glassy
no crystals because it cools so fast, ex: obsidian and pumice
pumice
vesicular looking because of trapped air (like a sponge)
what are the two compositions?
felsic and mafic
felsic
contains a lot of feldspar and silica, usually light in color and less dense, ex: granite
mafic
contains large amount of magnesium and ferrum (iron) rich silicates, usually dark in color and more dense, ex: basalt
what are the most common igneous rocks?
granite and basalt
granite
intrusive (cools underground), coarse grained (big crystals), felsic (light in color), continental crust
basalt
extrusive (cools underground), fine grained (small crystals), mafic (dark in color), oceanic crust
volcano
as rock melts it becomes less dense and rises. if the molten rock can escape through a crack or think spot and creates a volcano
magma
molten rock that is below earth's surface
lava
molten rock that is on earth's surface
where does the heat come from?
radioactive decay of elements, trapped heat from when the earth was formed, friction from the plates sliding
where do volcanoes form?
divergent boundary, convergent boundary, hot spots
divergent boundary
where plates are pulled apart
rift
on land
seafloor spreading
in ocean (mid-ocean ridge)
convergent boundary
where plates are pushes together
what has a convergent boundary?
trenches, volcano island arcs, and coastal volcanoes
what is the ring of fire?
a ring of volcanoes that surrounds the pacific ocean and is due to convergent boundaries
hot spots
intraplate volcanoes are not at a plate boundary at all but in the middle of a plate
why does a hot spot occur?
because there is a small region deep down in the mantle plume that is hotter than normal magma and it leaks out
what places have hot spots?
hawaiian islands and yellowstone national park
what do the hawaiian islands show you?
how a plate has moved over a hot spot over the years
old islands
have dormant volcanoes that are unlikely to ever erupt again
young islands
have active volcanoes
what is a volcano?
an opening where magma erupts onto earth's surface as lava and/or other extrusive material
what are the three volcanic activities?
active, dormant, and extinct
active
erupting or showing signs or erupting
dormant
not active but could reawaken
extinct
extremely unlikely to reawaken
what are the two forms of eruptions?
explosive (convergent) and gentle (divergent)
what are the gases volcanoes put off?
water vapor, carbon dioxide, and sulfur
what can be ejected from volcanoes?
pyroclastic material, tephra, they can range in size from tiny dust particles to large volcanic bombs
what are pyroclastic clouds?
the combo of super heated gas and dust
what are the three types of volcanoes?
shield, cinder cone, composite (stratovolcano)
shield
usually form from basaltic lava, they are large, broad, and flat. usually less explosive. ex: hawaii
cinder cone
they are formed from dust, ash, and cinder. they have steep slopes, single eruption that lasts from a few weeks to a few years. they are small in size.
composite (stratovolcano)
they are symmetrical. they have layers of lava and pyroclastic material. they are the most dangerous (silica rich), most are in the ring of fire
what are the four volcanic landforms?
crater, caldera, volcanic necks, lava plateaus
crater
a depression at the top of a volcano
caldera
formed when a volcano is no longer active and the top of the magma chamber starts to collapse in on itself
volcanic necks
formed when magma hardens in the main pipe and the volcano erodes away but leaves the pipe
lava plateaus
extensive areas of flood basalt; often at fissures where there is flood lava
what are the four igneous intrusions?
plutons, sills, laccolith, dikes
plutons
structures formed from magma cooled underground
sills
cooled magma between parallel layers of sedimentary rock
laccolith
similar to sills but in a lens shape because of thicker magma
dikes
magma moves into a break in the rock layers
what are the five volcano side effects?
hot springs, mudflow, geyser, geothermal, earthquakes
hot springs
groundwater is heated by magma and forced to surface
mudflow
volcano melts ice and combines with debrisgey
geyser
heated groundwater turns into steam
geothermal
heat can be harvested for energy