Rocks
A particular chemical combination that has a hardness, density, and definite crystal structure of its own is called a/an _________ .
mineral
__________ rocks are formed by the cooling and solidification of molten rock.
Igneous
_________ rock is formed at or near Earth’s surface by the accumulation and lithification of particles of gravel, sand, silt, and clay that were eroded from already existing rocks.
Sedimentary
_________ rocks are formed from igneous and sedimentary rocks by Earth’s forces that generate heat, pressure, or chemical reaction.
Metamorphic
The first step in the rock cycle, these rocks are also known as primary rocks.
Igneous Rocks
Rocks are composed of particles that contain various combinations of such common ___________ as oxygen, silicon, aluminum, iron, and calcium, together with less-abundant varieties of these.
elements
_________ igneous rocks are formed below ground level by the solidification of magma
Intrusive
If the organic material forms mainly from decomposing vegetation, it can develop into a sedimentary rock called bituminous ______ .
coal
The internal Earth forces may be so great that ______ and _______ change the mineral structure of a rock, forming new rocks.
heat and pressure
Sun, rain, frost, and wind are breaking down even the most solid of the rocks into smaller bits before they are taken away. __________ is the breaking down or dissolving of rocks and minerals on Earths surface.
Weathering
A mineral's hardness is a measure of its relative resistance to scratching, measured by scratching the mineral against another substance of known hardness on the ________ Hardness Scale.
Mohs
________ igneous rocks are created above ground level by the solidification of lava.
extrusive
Sedimentary rocks evolve under water in horizontal beds called ______ .
strata
Metamorphic is the ________ common type of rock.
least
Once a rock has been broken down, a process called _______ transports the bits of rock and minerals away.
erosion
Although one can classify rocks according to their physical properties, the more common approach is to classify them by the way they formed. Accordingly there are _______ main groups of rocks.
three
The lava that oozes out onto the Earth’s surface and makes up a large part of the ocean basins becomes the extrusive igneous rock called ______ , the most common rock on the Earth’s surface.
basalt
Sedimentary rocks also derive from organic material, such as coral, shells, and marine skeletons. These materials settle into beds in shallow seas, forming ________ .
limestone
________ , under certain conditions, may become marble.
Limestone
Rocks underground melt to become ______ .
Magma
A ______ is so hard it ranks as a 10 on the Mohs scale–the highest level of hardness.
diamond
Some igneous rocks may be glassy, as is _______ . The glassiness occurs when lava meets standing water and cools suddenly.
obsidian
_________ is when deposited sediments are smooshed together by the weight of water and other sediment that has settled on top of it. _________ is when the sediments are glued together by the minerals that come out of supersaturated water. (Two answers)
Compaction and cementation
These classes of rocks may become metamorphic rocks.
Igneous, sedimentary, and metamorphic rocks
The complex process whereby freshly deposited loose grains of sediment are converted into rock. (root of this word from the Ancient Greek word meaning 'rock')
lithification