ROCKS Flashcards
(midterm coverage)
Are the solid constituents of the earth’s crust either firm, earthy & granular. They are aggregates of one or more minerals.
ROCKS
is the science that deals with the study with the mode of occurrence, composition, classification and origin of rocks and their relations to geological processes & history.
Petrology
deals with the origin of rocks.
Petrogenesis
Origin of Rocks (6)
- Cooling of magma (molten rock) which issues from considerable depths below the earth surface.
- Precipitation of inorganic materials from water.
- Deposition of shells of various organisms.
- Condensation of a gas containing mineral particles
- Disintegration of other rocks and subsequent recombination of the resulting minerals to form new rock types.
- Action of intense heat and/ or pressure on pre-existing rock types.
Three Classifications of Rocks
- Igneous rocks
- Sedimentary rocks
- Metamorphic rocks
are formed from a once-hot, molten mass known as a magma or lava which cooled & crystallized into rock made up of aggregates of interlocking silicate minerals
Igneous Rocks
Igneous rocks occur in two general forms based on deposition:
- Extrusive Igneous Rock (volcanic rocks)
- Intrusive Igneous Rock (plutonic rocks)
Volcanic rocks are usually ____________, whereas plutonic rocks are ______________.
fine grained;
medium or coarse grained
are also called volcanic rocks that are formed at the earth’s surface as a result of volcanic activity. This activity is associated with mountain-building forces within the earth. If the rocks fracture as a result of the mountain – building forces, for example- the pressure may be released, and a sizable volume of rock will melt. The resulting magma will be forced through the fractures to the surface, forming a volcano.
Extrusive Igneous Rocks
are also called plutonic rocks, crystallized from magma that cool or hardens within the earth. The magma cools slowly resulting to the formation of coarse-grained igneous rocks.
Intrusive Igneous Rocks
In a widely accepted silica-content classification scheme, rocks with more than 65 percent silica are called _______
felsic
In a widely accepted silica-content classification scheme, rocks with between 55 and 65 percent silica are ____________
intermediate
In a widely accepted silica-content classification scheme, rocks with between 45 and 55 percent silica are ____________
mafic
In a widely accepted silica-content classification scheme, rocks with less than 45 percent are __________.
ultramafic
are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth’s surface, followed by cementation.
Sedimentary rocks
is the collective name for processes that cause these particles to settle in place.
Sedimentation
Types of Sedimentary Rocks
- Clastic sedimentary rocks
- Organic sedimentary rocks
- chemical sedimentary rocks
- bioclastic sedimentary rocks
are composed of fragments of weathered rocks, called clasts, that have been transported, deposited, and cemented together. These rocks make up more than 85 percent of all of this rock type. This category includes sandstone, siltstone, and shale.
Clastic sedimentary rocks
consist of the remains of plants or animals. Coal is an ____________ made up of decomposed and compacted plant remains.
Organic sedimentary rocks
They form by direct precipitation of minerals from solution. Rock salt, for example, forms when salt precipitates from evaporating seawater or saline lake water.
Chemical sedimentary rocks
Most limestone is composed of broken shell fragments. The fragments are clastic, but they form from organic material. As a result, limestone formed in this way is called a ______________.
Bioclastic sedimentary rocks.
refers to processes that convert loose sediment to hard rock.
Two of the most important processes are compaction and cementation.
Lithification