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Earth Sciences 1022A/B Study Guide - Final Guide: Permafrost, Aretes, Solifluction


Department
Earth Sciences
Course Code
EARTHSCI 1022A/B
Professor
Stephen R Hicock
Study Guide
Final

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Intro to physical geology and plate tectonics
1)What is geology important for?
-energy and natural resources, solving environmental problems, building cities and
highways, predicting and protecting against natural disasters (earthquakes, volcanic
eruptions, landslides, floods)
2) Define uniformitarianism.
-fundamental principal: “the present is the key to the past”
3) How is geologic time measured?
-in billions of years
4) How long ago was the Big Bang?
-14 billion years ago
5) How might the Earth have been formed? (it’s a theory)
-nebular theory
-5 billion years ago a solar nebula of hydrogen and helium gravitationally contracted into
a rotating disc with our Sun at the center, and the planets and moons revolving around it
6) Within the disc, how did the Earth continue to evolve?
-Through many collisions of rocky metallic fragments into a rocky sphere divided into a
dense core, large mantle, and lighter crust
7) What are plate tectonics?
-The crust and uppermost mantle eventually split into rigid plates of lithosphere (sphere
of rock) that movie over Earth’s surface above the soft asthenosphere (weak sphere) by
continental drift
8) What is the continental drift based on?
-The fit of continents (ie. South America, Africa, and other continents fit well together at
900m depths which coincides with the edge of their continental shelves
9) Explain the fossil evidence of this theory
-The different continents have the same type and aged fossils, even though ocean basins
separate them
10) List the last three supporters of this theory
-Rock types and structural similarities (match when continents are fit back tg)
-Paleo climates (evidence of ancient glaciations in warm areas of today show the pattern
of a single ice sheet if continent were refitted back together)
-Ancient coal fields (that formed in tropical swamps now occur in areas of cold climate)
11) Where does most geologic activity (earthquakes, volcanoes) occur?
-Plate boundaries
-ESPECIALLY at convergent boundaries where denser oceanic lithosphere descends
beneath lighter continental lithosphere
12) What happens at depth?
-It melts to produce magma, which rises to the surface and erupts as volcanoes, which in
turn are eventually eroded and the sediment carried by streams to the ocean again
13) Explain the Earth System.
-Earth is a dynamic planet (system) of interacting hydrosphere, atmosphere, biosphere
and geosphere (solid earth); matter (molecules) is recycled with changing conditions of
depth (pressure), temperature, and rock type within Earth’s crust (ie. Convergent
boundaries)
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14) What do the rock cycle and plate tectonics produce together?
-Many different types of rocks that are made up of different minerals
Minerals
1) What are minerals?
-Solid chemical compounds that combine to form rocks
2) Where are they found and what do they vary in?
-Nature
-Vary in atomic bonding, molecular structure, and element composition
3) All of which determine…?
-Their chemical, physical properties and permit their identification
4) Over how many natural minerals are known?
-4700 HOWEVER, only 20 are dominant in the Earth’s crust
5) What are common minerals?
-Natural, solid compounds found commonly in earth’s crust
6) What are the most abundant?
-Silicates, which are made of silicon-oxygen tetrahedron (silica, (SiO4)-4) bonded to
various metallic cations
7) What do ferromagnesian (dark) silicates contain?
-Fe+2 and Mg+2
8) Give 4 examples of these minerals and examine their makeup
-Olivine: covalently-bonded silica tetrehedra surrounded by Fe, Mg cations; Fe, Mg
substitute for each other to form a group of minerals
-Pyroxene: Single chains of tetrahedra ionically bonded to metallic cations, nearly right
angle cleavage
-Amphibole: Double chains of tetrahedra ionically bonded to metallic cations, 120-degree
cleavage
-Biotite: Tetrahedral sheets ioncally sandwich K+, perfect platy cleavage
9) Give 3 examples of nonferromagnesian (light) silicates and examine their makeup
-Muscovite: tetrahedral sheets with perfect platy cleavage
-Feldspar: Strongly bonded 3-D network of silica tetrahedra, K variety is called
orthoclase and Ca-N group is called plagioclase
-Quartz: Made entirely of silica tetrahedra (SiO2) covalently bonded, hard, has no
cleavage
10) What are carbonates?
-Metals bonded to (CO3)-2 group to form minerals like calcite (CaCO3; used for lime,
cement) and Dolomite (CaMg(CO3)2)
11) What are halite and gypsum used for?
-NaCl=salt
-CaSO4 & H2O=plaster and drywall
12) How are halite and gypsum formed?
-By evaporation of ancient shallow seas and salt ponds
13) What do ores of metals include?
-Hematite (Fe2O3 iron ore), Sphalerite (ZnS, zinc ore), Galena (PbS lead ore), and native
gold & silver that are important to our economy
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14) Why do many minerals tend to occur together?
-They were formed under similar pressure and temperature conditions, but with different
combinations of elements
15) How can minerals be transferred into new minerals?
-By being transported to another part of the rock cycle: the new minerals form from
previous ones as pressure and temp conditions change in the new environment
Igneous rocks
1) How do igneous rocks crystallize?
-From molten silicate material called magma that forms at high temp and pressures deep
in the Earth
2) What happens to the magma?
-It rises through the crust and either reaches the surface by volcanoes (extrusive) or cools
below (intrusive)
3) What is the theory called that describes how magma evolves?
-Bowmen’s Reaction Series
4) What is discontinuous in this theory and what is continuous?
-Discontinuous (different molecular structures of olivine [single tetrahedra], pyroxene
[single chains], amphibole [double chains], biotite [sheets]
-Continuous (same plagioclase structure)
5) What does repeated crystal settling in a magma chamber result in?
-The melt crystallizing through a series of minerals according to their decreasing melting
temperatures
-Remaining crystals react with the melt that is enriched in lighter elements with them,
and then light crystals form from the remaining light elements, eventually to quartz
-THUS granite can ultimately evolve from an original magma having a basaltic
composition
6) What can it also change through? Explain.
-Assimilation (pieces of host rock fall into the magma and melt) and magma mixing
where one body of magma invades another, producing a composition intermediate
between the two
7) What is the range of rock composition?
-From dark (mafic, less silica) to light (felsic, more silica) minerals
8) What does texture entail?
-Size, shape, arrangement of crystals
9) How is aphanitic texture formed?
-Rapid cooling near the ground surface (cannot see separate minerals with naked eye)
10) Opposite?
-Phaneritic texture is formed by slow cooling below the surface (easily distinguish
separate minerals with naked eye)
11) Describe the last 3 kinds of textures
-Porphyritic: larger crystals surrounded by smaller ones
-Glassy: if lava was quenched do fast that crystals had no time to form
-Pyroclastic (Fragmental): when magma was ejected violently into the air then fel as
particles onto the ground
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