Rocks Flashcards
Neptunism
early concept presumed that rocks were originally deposited in a series of layers as a result of either chemical precipitation or deposition of material carried in suspension in the ocean
Plutonism
early thought that presumed that some rocks were formed directly by molten material that cooled and solidified on or below Earth’s surface
What are rocks made of?
minerals
What are minerals made of?
elements arranged in characteristic atomic structures
How are minerals categorized?
By the chemical elements they contain
What are the most common elements in Continental Crust?
oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium
What is an atom?
the smallest particle that retains the characteristics of an element
What is the atomic number?
the number of protons and electrons in an element
What are two types of bonds?
Ionic and covalent
What is ionic bonding
Forms due to the attraction between opposite charges; when one donates an electron to another
What is covalent bonding?
When atoms share electrons to achieve a stable structure
What are silicates?
silicon and oxygen; they form a pyramidlike structure known as the silica tetrahedron; minerals that contain both silicon and oxygen
What are minerals?
naturally occurring inorganic solids of one or more elements that have a definite chemical composition with an orderly arrangement of atoms
How are minerals characterized?
crystal form, cleavage, hardness, and color
What is crystal form?
the shape of a crystal that a mineral forms when it is free to grow unimpeded
What is cleavage?
the propensity of a mineral to break alone one or more planes
What is hardness?
the resistance of a mineral to scratching
-Moh’s scale (1-10, diamond = 10 and can scratch anything below it)
Color? Dark vs Light
Dark colored rocks= green, dark green, black, dark brown
Light colored rocks= white, pink, gray, transluscent
Other properties used in identifying rocks?
Luster-how light is reflected from a mineral
Streak-the mark formed when a mineral is scratched across an unglazed piece of porcelain
How do igneous rocks form?
These rocks form from the cooling of melted rock (magma). They can be classified as volcanic or plutonic.
How do volcanic igneous rocks form?
A type of igneous rock that forms when magma in Earth’s interior rises to the surface through pipes or fractures in the crust. These cool slowly and have smaller crystals.
How do plutonic igneous rocks form?
A type of igneous rock that forms below Earth’s surface. The features they form are called plutons which remain hidden from view until erosion or tectonic plate movement uplift them or exposes them at the surface. These cool slowly and thus have bigger crystals
What does size of mineral crystals determine?
Where the mineral developed. Bigger crystals means it cooled underground slower whereas smaller crystals means it cooled faster at the surface
Mafic Rocks
igneous rock rich in magnesium and iron
ultramafic rocks
igneous rock with a very low silica content and are composed of greater than 90% mafic minerals (dark colored, high magnesium and iron content)
intermediate igneous rocks
igneous rocks that have 5-20% quartz
felsic rocks
igneous rocks that are relatively rich in elements that form feldspar and quartz and are silica rich. They are usually lighter in color.
How are sedimentary rocks formed? What are the three types?
Rock type that is formed from deposits of pre-existing rocks or pieces of once-living organisms that accumulate on earth’s surface. Three types: clastic, chemical, and biochemical.
What are clastic sedimentary rocks?
A type of sedimentary rock that is composed of sediments that form when rocks break apart at or near Earth’s surface. Majority of all sedimentary rocks.
What are chemical sedimentary rocks?
A type of sedimentary rock that are crystallized from a solution (eg-seawater) as a result of changing conditions. Eg-evaporation of seawater in which salt precipitates from the water and sinks to the bottom of the lake or ocean forming a layer of halite
What are biochemical sedimentary rocks?
A type of sedimentary rock that is formed by the actions of living organisms or are composed of the remains of dead organisms. Eg- massive limestone coral reefs have formed because of the actions of the coral organisms. Chalk forms from the skeletons of marine microorganisms known as coccolithopores. Coal forms from compacted remains of dead plants
How is weathered material classified?
Material that is known as sediment and is classified on the basis of its grain size. Eg-clay and silt are small sediment particles
What is erosion?
The process by which sediment is removed from its place of origin by running water, winds, or glaciers
Lithification
When clastic sediments are deposited when the velocity of the transporting medium drops. Large material is deposited first followed by smaller and smaller particles as the velocity drops.
The processes of compaction and cementation that convert sediment into a sedimentary rock
How are fossil fuels formed?
From sedimentary rocks which form from decayed organic material. Oil, coal, and natural gas are the most common products of this process. Oil and gas form from microscopic marine animals while coal forms from decayed plant material. The formation of these types extracts carbon from the environment and releases it as carbon dioxide, contributing to elevating greenhouse gas concentrations.
Where are the three principal coal-producing regions in the United States?
Appalachian base states (Ohio, eastern Kentucky, West Virginia, Pennsylvania), interior states (Indiana, Illinois, western Kentucky), and Great Plains/Rocky Mountain States (Montana, Wyoming, North Dakota, South Dakota, Colorado)
How are metamorphic rocks formed? What are the two types?
Rocks that form due to changes in mineral composition or texture that occur in solid rock as a result of increasing temperature or pressure. The two types are contact metamorphism and regional metamorphism
How does contact metamorphism occur?
Type of metamorphic rock that occurs when rocks come in contact with a heat source (usually a magma body). Eg-marble forms when limestone is heated to high temperatures. Both marble and limestone have the same composition however marble typically has larger grains
How does regional metamorphism occur?
Type of metamorphic rock that occurs when rocks undergo increased temperatures and pressures typically associated with plate tectonic processes that form mountains. Rocks formed this way are classified by the size of minerals that form when they change from the original rock
What are foliations?
a geometric orientation found in regional metamorphic rocks that generates an alignment of minerals into sheets. Not all rocks form this- for example rocks that lack sheetlike minerals don’t generate the parallel alignment of minerals necessary eg-sandstone changing into quartzite and limestone changing into marble doesn’t form these
What are mineral resources?
A term used to refer to nonfood, nonfuel resources such as metals and industrial minerals. Their development depends on more than just the presence of mineral deposits
Ore
a rock containing economic concentrations of metallic minerals
What are key in hydrothermal mineral deposits?
magma and water are key ingredients for this
Where do hydrothermal deposits form?
In oceans where water is readily available. Magma rises along the oceanic ridges and cold bottom waters from the ocean floors can infiltrate the oceanic crust through networks of narrow fractures.
They can also form on land when metal-rich fluids are expelled from magma chambers to form veins that fill fractures in the surrounding rock
What are magmatic mineral deposits?
when minerals are concentrated in narrow zones within igneous rocks. Caused by cooling processes inside magma chambers. Formed at high temperatures before the magma solidifies
What is crystal setting?
the process in which minerals crystallize from magma. They are heavier than the surrounding magma and thus sink to the bottom of the magma chamber, forming an enriched layer
What are residual mineral deposits?
ores left behind in sufficient concentrations of economic minerals so they form ores. Caused by water flowing through rocks in or near the land surface. These are formed most rapidly in areas with rapid weathering rates such as the tropics.
What are placer deposits?
A natural recycling of older mineral deposits that are found in present-day streams or in ancient stream deposits. The stream flow serves to sort and concentrate the minerals. Heavier minerals are among the first materials to be deposited thus these deposits may be found easily, often deposited at the inside of stream beds or at the stream mouth.
phaneritic igneous rocks
igneous rocks that have entirely large visible crystals
porphyritic igneous rocks
igneous rocks that have mixed crystal sizes
aphanitic igneous rocks
igneous rocks that have entirely microscopic crystals
protolith
the original, unmetamorphosed rock from which a given metamorphic rock is formed
