Geology Exam 1

Is color a reliable identification feature for minerals?

Yes. Color of a mineral is usually its most noticeable property. Some minerals occur in shades of only one color, so that color can be used as a clue to their identity. -Quarts is a common mineral that can occur in many different colors.

What do microcrystalline and cryptocrystalline mean?

You cannot see crystals in crystalline textured rocks with the naked eye. You need a microscope

How are minerals classified?

minerals are classified based on their chemical composition. They are divided into classes according to their dominant anion or anionic group (e.x., halides, oxides, and sulfides, carbonates, halides, silicates).

Examples of minerals that are carbonates? Sulfides?

*Carbonates* (fizz in acid) -Calcite -Aragonite *Sulfides* -Pyrite (fools gold) -Galena

Examples of minerals that are silicates?

*Most important and most common group of minerals, most complex and abundant* -Quartz (*most common mineral in the crust*) -Feldspar (Potassium feldspar & Plagioclase feldspar) -Pyroxene and Amphibole -Mica

What is lithosphere? What are its properties? What are the two types of lithosphere?

*the crust and lithosphere are not the same thing* -Lithosphere: Crust + moho + uppermost mantle -2 types: Continental lithosphere (thin part) & oceanic lithosphere (thick part)

How do we know the Earth is 4.55 billion years old? Does this number come from Earth rocks? If not, where does the number come from?

-Archbishop Ussher (1650's) -Count Buffon (mid 1700's) -Curvier Cearly (early 1800's) -Darwin on the origins of species (1859) -Lord Kelvin/therodynamic calculations (1800's) -Joly/saltiness of the ocean (1890) -No, it comes from dating of meteorites

What is asthenosphere? What are its properties?

-Asthenomsphere: The viscous, goey layer under the plates. -It's a zone of Earth's mantle lying beneath the lithosphere and believed to be much hotter and more fluid than the lithosphere.

What is catastrophism? Is it still accepted?

-Catastrophism: The theory that the Earth had largely been shaped by sudden, short-lived, violent events, possibly worldwide in scope. -geological epochs had ended with violent and sudden natural catastrophes such as great floods and the rapid formation of major mountain chains. -tested and shown to be wrong, not accepted.

What is clastic texture? What is foliated texture? What is glassy texture? What is vesicular/frothy texture?

-Clastic: Loose/grains. Usually form from volcanic eruptions. -Foliated: Repetitive layering in metamorphic rocks. Each layer may be as thin as a sheet of paper, or over a meter in thickness -Glassy: No crystals at all, extremely rapid cooling -Vesicular/frothy: Has holes that were originally gas bubbles in lava

What is cleavage? What is fracture? What is conchoidal fracture?

-Cleavage: Minerals break along uneven surfaces, along perfectly flat surfaces, or combinations of both uneven and flat surfaces. The flat surfaces are called cleavage planes, and the uneven surfaces are called fracture surfaces. -Fracture: Nonplanar, nonparallel surfaces along which minerals and other substances may break in addition to cleavage. Quartz and glass are examples of materials that fracture and lack cleavage. -Conchoidal: Smoothly curved surfaces present when minerals break

What are the characteristics of coal, limestone (fossiliferous limestone), and chalk?

-Coal: Remains of plants in swamps -Limestone: All calcite (bubbles in acid), mix of whole fragmented fossils -Chalk: Type of limestone, has calcite, 100% microfossils

What are the characteristics of conglomerate, breccia, sandstone, siltstone, and shale?

-Conglomerate: Mix of large and small grains (*round grains*) -Breccia: Mix of large and small grains (*angular/sharp grains*) -Sandstone: Composed of sand grains -Siltstone: Composed of silt-sized grains -Shale: Composed of clay-sized grains

What is the continental drift hypothesis? Who proposed it? When? What was the evidence? What is Pangaea? Was continental drift hypothesis accepted by scientists at the time? What idea replaces it now? When did it become a viable theory?

-Continental drift hypothesis: The obvious match of the Americas to Africa and Europe (they used to be fused together) -Alfred Wegener proposed this idea in 1912 -Wegener's evidence: Matching shorelines, similar fossils in areas that are now far apart, similar stratigraphics (layered rocks) in areas now far apart, matching mountain ranges, similar paleoclimates (ancient climates) in areas now far apart -Pangaea: "all earth" Name of the supercontinent -The CD hypothesis wasn't accepted at the time (in 1912) so the plate tectonic theory replaced it in 1960.

What is the crust? What are the two types of crust? What rock type is most common in each of the two types of crust?

-Crust: The outermost solid layer of the earth -Two types: 1. Thin, heavy oceanic crust that lies underneath the seafloor, and 2. thicker, lightweight continental crust that under landmass. -Common rocks: The oceanic crust is composed primarily of basalt (black lava rock), and the continental crust is composed primarily of granite.

What is crystalline texture?

-Crystalline: When the rock has crystals in it. there are 4 kinds of crystalline textures-- *Aphanitic*: Small crystals (can't see with naked eye-microcrystalline/cryptocrystalline), quick cooling *Phaneritic*: Large crystals (can see with the naked eye), slow cooling *Porphyritic* Mix of large crystals (phenocrysts) and small crystals (groundmass), slow cooling at first, then quick cooling.

What are crystals? What are minerals? Is coal a mineral? Is oil a mineral? Are there minerals in breakfast cereal?

-Crystals: Sold, orderly arrangement of atoms -Minerals: Naturally occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. -Oil is Not a mineral bc it's a liquid & not natural -Coal is NOT a mineral bc it's organic -There ARE minerals in cereal

Examples of halite minerals? Does Ohio have any halite?

-Cubic cleavage and crystals -Yes, common in north east Ohio

What are divergence and convergence plate movements? What happens during each movement?

-Divergence: 2 plates moving away from each other. -What happens: New oceanic crust is created at mid-ocean ridges (MOR), and seafloor spreading. -Convergence: 2 plates moving towards each other What happens: Crust is destroyed through subduction, collision and transform movements

What is double refraction? Example of a mineral that shows this?

-Double refraction: The separation of a ray of light into two unequally refracted, plane-polarized rays occurring in crystals in which the velocity of light rays is not the same in all directions. -Mineral: Calcite

When did the Pangaea supercontinent exist? How did Pangaea break apart - how does any continent break apart?

-Existed: 250 million years ago -How it broke apart: Heat currents in the upper mantle and rifting/plate movements -How any continent breaks up: Forces (heat currents), earthquakes, and plate movements (divergence & convergence)

What is an extrusive igneous rock? What is an intrusive igneous rock?

-Extrusive: formed near or at the surface, or on seafloor. Relatively quick cooling of lava -Intrusive: formed deep underground, relatively slow cooling of magma

What is felsic? How do you tell if a rock is felsic?

-Felsic: Dominated by potassium feldspar and quartz -Light colored

What is geology? What does it involve?

-Geology: Study of the earth, not just the study of rocks -Involves: the geosphere (solid part of earth- metamorphic, sedimentary & igneous), hydrosphere (water part of earth), cryosphere (ice/glaciers), atmosphere (air/weather), biosphere (life forms)

How is mica best identified? What are the two common mica varieties?

-Has perfect cleavage, can be peeled into ultra thin flexible sheets -2 types: -Muscovite (clear) -Biotite (black) *Both common in granite*

What are hotspots? Examples?

-Hotspots: A location on the Earth's surface that has experienced active volcanism for a long period of time. They breakup and cause rifting of continents. -They were thought to be caused by a narrow stream of hot mantle convecting up from the mantle-core boundary called a mantle plum. -Example: East African Rift Valley

How do siliciclastic sedimentary rocks form? What is their texture? What are they commonly composed of?

-How siliciclastic rocks form: From solidification of loose sediments -Texture: Clastic -Composed of: Weathering and erosion of any pre-existing bed rock (silicate minerals)

How do biogenic sedimentary rocks form? What is their texture?

-How they form: made up of animals, plants, microbes etc. (fossils) -texture: Most are clastic, some crystalline

What is an hypothesis? What is a theory?

-Hypothesis: A rough idea or educated guess -Theory: Rigorously tested hypothesis or set of hypotheses. Theories are mostly right, unlike hypotheses. They are one step below absolute certainty

What is luster? What are the two common types of luster?

-Luster: A description of how the surface of a substance reflects light. -2 types: Metallic luster (Silver, gold or copper sheen as displayed by metals.) Non-metallic luster (A luster unlike a metal.)

What is a mid-ocean ridge (MOR)? What is seafloor spreading? What happens at a mid-ocean ridge?

-MOR: An underwater mountain range, formed by plate tectonics. -What happens: This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary. -Seafloor spreading: Occurs along mid-ocean ridges where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.

What is the core? What's it made of? What are its characteristics? What is the inner core? What is the outer core? What's the difference?

-Made of: Earth's Core is thought to be composed mainly of an iron and nickel alloy. -Characteristics: The core is earth's source of internal heat because it contains radioactive materials which release heat as they break down into more stable substances. Composed of metal -Inner core: Is a solid even though its temperature is higher than the outer core. Here, tremendous pressure, produced by the weight of the overlying rocks, is strong enough to crowd the atoms tightly together and prevents the liquid state. -Outer core: Is a liquid because the temperatures there are adequate to melt the iron-nickel alloy.

What is mafic? How do you tell if a rock is mafic?

-Mafic: Dominated by plagioclase feldspar and pyroxene -Dark colored

Are these 3 groups of rocks evenly distributed in the crust? Which group is most abundant in the crust? Which group is least abundant in the crust?

-No, they are not evenly distributed. -65% of the crust is igneous rocks (*most common*) -8% of the crust is sedimentary rocks (*least common*) -27% of the crust is metamorphic rocks

What are the oldest known Earth rocks? Oldest known mineral/

-Oldest rock: Acasta Gneiss (4.03 billion yrs) and subsurface rocks (4.5 billion yrs) -Oldest mineral: Conglomerate (4.4 billions yrs)

What 8 elements are most common in the crust? Which 2 elements top the list?

-Oxygen (most common) -Silicon (most common) -Aluminum -Iron -Calcium -Nitrogen -Magnesium -Potassium

What is a pluton? What is a batholith? What is an igneous dike?

-Pluton: An igneous intrusion of any size or shape.. the largest kind is a *batholith* -Batholith- pluton greater than 100km^2 in size EX-- Sierra Nevada -Dike: Crack in rock filled with dried magma EX-- Great Dike of Rhodesia

What are the two types of feldspar?

-Potassium feldspar -Plagioclase feldspar *only difference b/w them is color*

What's a rock? How many groups of rocks are there? How are rocks grouped, or classified? What are the three groups of rocks?

-Rock: A a natural substance, a solid consisted of one or more minerals or mineraloids. -3 groups: Igneous, sedimentary & metamorphic -Igneous: Cooled from hot, molten rock (lava/magma -- *lava is at the surface, magma is deep below earths surface*) -Sedimentary: Form by solidification of loose sediments (Sand grains form into sandstone) -Metamorphic: Intense alteration of previously existing rocks (Granite forms into gneiss)

What is specific gravity? Example of a very heavy mineral?

-Specific gravity: The ratio of the weight of a substance to the weight of an equal volume of water. -Hefting is an easy way to judge the SG of one mineral relative to another. This is done by holding a piece of the first mineral in one hand, and holding an equal sized piece of the second mineral in your other hand. -Ex of heavy mineral: Copper, pyrite

What is streak? What is hardness? How is it measured? What's the softest mineral? What's the hardest mineral?

-Streak: Is the color of a substance after it has been ground to a fine powder -Hardness: A measure of resistance to scratching. A harder substance will scratch a softer one. -Measured from a hardness scale 1-10 (Mohs Scale Of Hardness.) Higher numbered minerals will scratch lower numbered minerals. -Softest mineral: Talc -Hardest mineral: Diamond

What is science? What are the features of science? How is science done?

-Study of all natural objects, processes and phenomena of the universe -Features of science are based on facts and observation from nature, NOT based on beliefs. The goal is to predict events and have falsifiable (testable) scientific ideas. -There's more than one way of doing science. One can gather facts and observations, explain how or why something works and why it does, and make a hypothesis

What are subduction, collision and transform movements? what happens at those convergences? What are some examples of them?

-Subduction: One plate dives below another plate -What happens: Formation of volcanic arcs -Examples: Japan, Philippines, Indonesia, Andes Mountains, Aleution islands of Alaska, Cascade range -Collision: 2 plates crash into each other -What happens: Formation of mountains and continental crust can't be subducted. -Examples: Himilayas, Alps, Urals, Appalacians -Transform movement: 2 plates sliding past each other -What happens: Crust is not created nor destroyed -Example: San Andreas Fault

What is texture?

-Texture: refers to the physical makeup of rock—namely, the size, shape, and arrangement (packing and orientation) of the discrete grains or particles of a rock.

What is ultramafic?

-Ultramafic: Dominated by olivine and/or pyroxene -Green or dark colored

What is uniformitarianism? Who proposed it? When?

-Uniformitarianism: Slow incremental changes, such as erosion, created all the Earth's geological features. It held that the present was the key to the past, and that all geological processes (such as erosion) throughout the past were like those that can be observed now. -James Hulton, Charles Lyell

How old is the universe, in years? How old is Earth, in years? How old are the oldest known fossils? How old are the oldest known fossils of modern humans?

-Universe: 13.799 billion yrs old -Earth: 4.55 billion yrs old -Oldest known fossils: 3.7 billion yrs old -Oldest know human fossils: 315,000 yrs old

What is the average speed of tectonic plates?

5 cm/year

What is actualism?

All processes active now, were active in the past BUT with varying intensities

Where do almost all earthquakes occur?

At, or near plate tectonics (ex: Japan, Philippines)

Example of a mineral that bubbles in acid?

Calcite

Most igneous rocks have what texture?

Crystalline

What are some crystal shapes that mineral can take?

Dodecahedron, tubular, cube, tetrahedron, pyritohedron, octcahedron, hexagonal prism, hexagonal pyramid, rhombohedron, prismatic, scalenohedron

Plaster & wallboard are made using what sulfate mineral?

Gypsum

Examples of minerals that are oxides?

Gypsum, Silica, potassium feldspar, plagioclase feldspar

What is an example of a mineral that has a salty taste?

Halite

What force causes plates to move?

Heat

Example of a mineral that is magnetic?

Magnetite

What is the mantle? What's it made of?

Mantle: Very thick layer surrounding the core. It has a lower mantle (warm and soft) and an upper mantle (cool and brittle) Made out of: Solid, heavy rock (peridotite)

What are the youngest Earth rocks?

New rocks are forming all the time but usually lava rocks.

Do all hotspots break apart plates? Examples?

No, the Hawaii and Yellowstone hotspot are just big volcanoes.

What are the origins of minerals? What is the most common origin of minerals?

Origins: -Cooling of magma or lava (most common) -evaporating water -intense alteration from previously existing minerals through heat, pressure and chem. alteration

How many minerals have been named?

Over 5,200

What is "fool's gold"?

Pyrite

Examples of minerals that are elements?

Pyrite, Galena, Gypsum, Halite, Flourite, Potassium Feldspar, Plagioclase Feldspa, silica

What's the # 1 most common mineral in the crust?

Quartz

What is silica?

Silica is the name given to a group of minerals composed of silicon and oxygen, the two most abundant elements in the earth's crust.

Which mineral group is the largest, most abundant, and most complex?

Silicates

What is the Moho?

The boundary between the Earth's crust and its mantle.

What is the relationship between cooling rate & crystal size in igneous rocks?

The slower the cooling, the larger the crystals. The faster the cooling, the smaller the crystals.

What is the Pleistocene?

The time period that began about 2.6 million years ago and lasted until about 11,700 years ago. The most recent Ice Age occurred then, as glaciers covered huge parts of the planet Earth.

What are the 9 largest plates on Earth? Which is the largest plate at present?

1. Pacific Plate (largest) 2. Nazca Plate 3. Eurasian Plate 4. Antarctic Plate 5. North American Plate 6. African Plate 7. Australian-Indian Plate 8. Philippines Plate

How large is the Earth?

196.9 million mi²

What is the rift geometry formed when hotspots tear apart continents?

3 tear pattern (triple junction)