Geology 103 - Mid Term (Kansas State)

Aphanitic IGNEOUS ROCKS

Is a fine-grained texture, such that nearly all the crystals making up the rock are invisible to the naked eye.

Lava

Lava is magma that reaches the surface of our planet through a volcano vent.

Rocks in other rocks are older than the rock its within

Law of Intrusion?

Rock units can be in multiple locations

Law of Linear Contious?

Layers on bottom older, layers on top younger

Law of Superposition?

Felsic IGNEOUS ROCKS

Light colors, including white, light gray, tan and pink, indicate a felsic composition. Felsic compositions are rich in silica (SiO2)because they are composed largely of high-silica minerals such as quartz, potassium feldspar, and sodium-rich (white) plagioclase, with lesser amounts of biotite, muscovite and/oramphibole

Compositional types of igneous rocks

Felsic Intermediate Mafic Ultramafic

d. Olivine

An ultramafic peridotite would contain a high proportion of which minerals? a. Pyrite b. Quartz c. Plagioclase d. Olvine

Color

Color is one of the most obvious physical properties, but it can also be one of the least reliable as a diagnostic tool, especially for nonmetallic minerals. Minerals are colored because its internal crystal structure absorbs certain wavelengths of incident light.The color we perceive is produced by the wavelengths of light that were not absorbed. The same mineral can range in color from clear (or colorless)to black, which is why it's not a good idea to rely on color alone for mineral identification. Such color variations can arise because of the presence or absence of compositional impurities or defects in the crystal structure. Color due to impurities can be important to the value of certain minerals. The mineral beryl, when colorless, is of little value; but when it contains trace amounts of chromium it appears deep green and is called emerald.Similarly, blue corundum is known as sapphire and deep red corundum is called ruby.

Characteristics of Igneous Rocks

Compositional types & Textures

Mafic (and ultramafic) IGNEOUS ROCKS

Dark colors, such as black and dark brown, indicate a mafic or ultramafic composition. Mafic compositions are poor in silica, because they have a high proportion of minerals that are low in silica: olivine and pyroxenes. Instead, these minerals are rich in iron(Fe) and magnesium (Mg). Calcium-rich (dark gray) plagioclase is also a common constituent of mafic rocks, but is absent from ultramafic rocks

a. Phaneritic

Extrusive igneous rocks may exhibit which of the following igneous textures? a. Phaneritic b. Plutonic c. Granitic d. Glassy

c. Absolute Dating

Fossils (biostratigraphy) are used in which type of dating? a. Relative Dating b. Sequential Dating c. Absolute Dating d. Radiometeric Dating

Hardness

Hardness is a measure of how resistant a substance is to being scratched. A harder mineral will scratch a softer one, while the reverse is not true; two minerals of equal hardness can scratch each other. Hardness is measured on a scale of 1 to 10, called the Mohs Hardness Scale. The Mohs scale is a relative scale, not an absolute one, so a diamond is not ten times harder than talc, for example.

a. Unit A; Law of Superposition

If four rock layers are deposited in sequence with Unit D at the bottom of the sequence and Unit A at the top of the sequence, which unit is youngest and why? a. Unit A; Law of Superposition b. Unit D; Law of Superposition c. Unit A; Law of Lateral Continuity d. Unit D; Law of Lateral Continuity

Extrusive

Igneous rocks cool from lava rapidly because they form at the surface, so they have small crystals.

Intrusive

Igneous rocks cool from magma slowly because they are buried beneath the surface, so they have large crystals.

d. Lithification

In the formation of sedimentary rocks, compaction and cementation are part of the process of ________. a. Erosion b. Weathering c. Deposition d. Lithification

Intermediate IGNEOUS ROCKS

Intermediate compositions have an intermediate color, often gray or consisting of equal parts of dark and light mineral. They are composed largely of minerals such as (light gray)plagioclase, biotite, and amphibole. There is a continuum across the compositional range from ultramafic to felsic, so some high-silica minerals, such as quartz, may be present in intermediate rocks, as well as some low-silica minerals, such as pyroxene

What are the physical properties of minerals?

Luster Color Hardness Streak Crystal Form Cleavage and Fracture Smell Other

Luster MINERALS

Luster is the manner in which light is reflected from a mineral.In most minerals,some light can pass into the mineral and is reflected from within it. Such minerals are transparent or translucent. This internally reflected light gives the mineral a non-metallic luster. In some minerals, no light at all can penetrate the crystalline structure, so all the reflected light comes from the surface, resulting (usually) in a 'hard' glint or glitter that we call a metallic luster.Luster varies over a wide spectrum, and so additional terms are often used to provide greater descriptive detail: vitreous, adamantine or glassy (very shiny), to silky, pearly, satiny, resinous, greasy or waxy (progressively less shiny), to dull or earthy (refers to a powdery surface with no shine at all).

b. Contact

Metamorphism that occurs on a smaller, localized scale is known as __________ metamorphism. a. Regional b. Contact c. Hydrothermal d. Foliated

Textures of igneous rocks

Phaneritic Aphanitic Pyroclastic Vesicular Porphyritic Glassy

d. Immature

Sediments that are angular are very poorly sorted are said to be: a. Young b. Mature c. Submature d. Immature

Streak

Streak is the color of a mineral when powdered. It can be observed by scratching the mineral on a porcelain plate, called a streak plate. Note that minerals harder than porcelain have no streak.

Pyroclastic IGNEOUS ROCKS

Texture is composed of a mixture of volcanic rock fragments, pumice and volcanic ash. These fragments can be very fine grained (ash), coarse grained (lapilli) or very coarse grained (bombs and blocks).

Porphyritic IGNEOUS ROCKS

Texture is composed of crystals of two different sizes in which larger crystals(phenocrysts)are set among smaller crystals(referred to as groundmass).Usually only one or two minerals will occur as phenocrysts. The smaller crystals represent all other minerals present, and may also include some of the same minerals as the larger crystals.

Vesicular IGNEOUS ROCKS

Texture means that the rock contains holes referred to as vesicles.The size of vesicles can range from barely visible to over 10 mm in diameter, and their shapes are usually rounded in cross section. Some vesicles are filled with secondary mineral precipitation, in which case they are called amygdules rather than vesicles. Anamygdaloidal texture can be distinguished from a porphyritic texture by the shape of the crystals. The minerals tend to be rounded in amygdules but angular in porphyries.

b. Conglomerates have rounded grains; breccias have angular grains

The difference between a conglomerate and a breccia is___________. a. Breccias have larger grains b. Conglomerates have rounded grains; breccias have angular grains c. Conglomerates have angular grains; breccias have rounded grains d. Conglomerates have larger grains

c. Diamond

The hardest mineral on Earth according to Mohs Hardness Scale is: a. Talc b. Garnett c. Diamond d. Plagioclase

Cleavage and Fracture

The planes along which a mineral tends to break are called cleavage. Not all minerals have cleavage but, where present, the number of cleavage planes is important. Any break that is not along a cleavage plane is called a fracture. Most fracture surfaces are irregular,but some minerals, such as quartz, will break along smooth, curved,and slightly rippled surfaces called conchoidal fracture.

Garnet, no cleavage, 5.5

What is the name? Does it have cleavage? What is the hardness?

Halite, 4 cubic, 3

What is the name? How many directions of cleavage does it have and what is the name of this type of cleavage? What is it's hardness?

Biotite, one/basal, non-metalic

What is the name? How many directions of cleavage does this have, and what is the name for this type of cleavage? What is it's luster?

Basalt, mafic, aphanetic

What is the name? Is it Mafic, felsic, intermediate, or ultramafic? What type of texture does it have?

Marble, Non-foliated, limestone

What is the name? Is it a metamorphic rock foliated or non-folliated? What is the sedimentary parent rock?

Sandstone, clastic, quartz

What is the name? Is it clastic, biochemical, or chemical? What is the primary mineral constituent?

Breccia, clastic, angular sorted

What is the name? Is it clastic, biochemical, or chemical? What is the rounding and sorting?

Coquina, biochemical, fossil shells

What is the name? Is it clastic, chemical, or biochemical? What did the particles in this rock originate as?

Schist, foliated, medium

What is the name? Is it foliated or non-foliated? Is it low, medium, or high grade?

Phylite, foliated, shale

What is the name? Is it foliated or non-foliated? What is the parent rock?

Pumice, igneous, vesicular

What is the name? Is it igneous, metamorphic, or sedimentary? What is its texture?

Granite, felsic, phaneritic

What is the name? Is it mafic, felsic, intermediate, or ultramafic? What is the texture?

Calcite, non-metalic, Rhombic

What is the name? What is its Luster? What is its cleavage?

Obsidian, felsic, glossy

What is the name? What is the composition? What type of texture does it have?

Quartz, 7, no cleavage

What is the name? What is the hardness? Does this mineral have cleavage?

Hematite, 7, rusty

What is the name? What is the hardness? What color is the streak?

Orthoclase, 5, non-matalic

What is the name? What is the hardness? What is the luster?

Galena, matalic, high specific gravity

What is the name? What is the luster? What is one special property?

Coal, Biochemical, plant matter

What is the name? is it clastic, biochemical, or chemical? From what material did this rock form?

Gneiss, Regional, high

What is the name? is it contact or regional metamorphism? Is it low, medium, or high grade?

b. Quartzite

Which of the following is an example of a non-foliated metamorphic rock? a. Slate b. Quartzite c. Schist d. Gneiss

c. Diorite

Which of the following is an example of an igneous rock of intermediate composition? a. Basalt b. Granite c. Diorite d. Peridotite

c. Deposition

Which of the following is never an agent of metamorphism? a. Pressure b. Heat c. Deposition d. Hydrothermal Fluids

a. Calcite

Which of the following minerals fizzes in HCL acid? a. Calcite b. Quartz c. Plagioclase d. Talc

c. Foliation

Which of the processes listed below is NOT involved in the formation of sedimentary rocks? a. Weathering b. Lithification c. Foliation d. Transportation

a. Plagioclase and Potassium Feldspar

Which two minerals exhibit a noticeable basal (1 plane) cleavage? a. Plagioclase and Potassium Feldspar b. Fluorite and Biotite c. Muscovite and Biotite d. Biotite and Sphalerite

Phaneritic IGNEOUS ROCKS

is a coarse-grained texture in which the whole rock is composed of crystals that are visible to the naked eye but not greater than 2 cm in maximum dimension.

Magma

is composed of molten rock and is stored in the Earth's crust

Glassy IGNEOUS ROCKS

textures occur in rocks that have cooled without crystal formation. As with some minerals, they tend to show conchoidal fracture surfaces with luster typical of shards of glass.