GEOG 101 Chapter 9: GEOG 101 Chapter 9

10 Pages
Unlock Document

Towson University
Geography and Environmental Planning
GEOG 101

GEOG 101 Chapter 9 Outline 9.1 • Hand specimen - a hand-sized piece of rock collected by geoscientists to more closely observe rocks • Criteria for a mineral o Naturally occurring o Inorganic solid o Ordered internal (crystalline) structure - atoms are arranged in a regular, repeating way o Relatively consistent chemical composition • Silicate minerals are the most common family of minerals - account for over 90% of the minerals in Earth’s crust (SiO ) o Quartz ▪ Generally transparent ▪ Hard material commonly occurring as well-formed crystals ▪ Comes in many different colors o Mica ▪ Breaks into flakes and sheets that are partially transparent and shiny ▪ Reflect light o Feldspar ▪ Two varieties - potassium and plagioclase ▪ Pink or cream colored o Mafic minerals ▪ Contain magnesium and iron ▪ Generally dark o Clay minerals ** ▪ Sheets that are weakly held together ▪ Important component of soil ▪ Expands when wet • Nonsilicate minerals do not contain silicon and cause many landscapes to be reddish o Carbonate minerals ▪ Contain carbon and oxygen bonded with other elements ▪ Most common is calcite o Oxide minerals ▪ Oxygen bonded with a metallic element ▪ Red in color o Salt minerals ▪ Halite (table salt) o Sulfide minerals ▪ Contain sulfur bonded with a metallic element ▪ Pyrite is most common ▪ Commonly forms cube-shaped crystals 9.2 • Sediment - grains and other fragments that originate from the weathering and transport of rocks, and the consolidated deposits that result from the deposition of this material o Glaciers - ▪ Carry a wide variety of sediment o Steep mountain fronts - ▪ Exhibit large, angular rocks the broke away and moved downhill through gravity o Sand dunes - ▪ Mostly sand shifted along by the wind o Beaches - ▪ Waves, sand, broken shells, and rounded well-worn stones o Seafloor - ▪ Mud and remains of swimming and floating creates at the bottom o Stream channels - ▪ Sand, bigger pebbles and cobbles • Magma - melted rock beneath the Earth’s surface • Lava - melted rock above the Earth’s surface • Magma chambers o Cools and solidifies rather than erupting o Forms granite and other rocks at depth o Heat may bake surrounding rocks, changing their form • Metamorphism - when temperatures and pressures are high deep beneath the surface, forces can squeeze and deform rocks (slowly flow, shear, and bend) into new atomic arrangements - involves changing a rock that is unstable • Sedimentary rock - a rock resulting from the consolidation of sediment • Igneous rock - a rock formed by solidification of molten material (magma) • Metamorphic rock - a rock changed in the solid state by pressure, deformation, or chemical reactions that modified a preexisting rock 9.3 • (1) Weathering o Surface rocks interact with sunlight, rain, wind, plants, and animals and are mechanically broken apart or altered by chemical reactions • (2) Erosion and Transport o Rock pieces removed by weathering can be stripped away from the surface by erosion and moved away from their source by glaciers, water, wind, and gravity • (3) Deposition o When kinetic energy associated with transportation decreases, sediment is dropped • (4) Burial and Lithification o Once deposited, sediment can be buried and compacted by the weight of overlaying material o Chemicals in groundwater can coat sedimentary grains with minerals and deposit natural cements that bind the grains • (5) Deformation and Metamorphism o After a rock has been formed, strong forces can squeeze it and fold its layers o Rock can also be heated and deformed to produce metamorphic rock • (6) Melting o Rocks exposed to high temperatures may melt to produce magma (magmatism) • (7) Solidification o As magma cools, it begins to solidify and harden o If crystals form during solidification, the process is called crystallization • (8) Uplift o At any point in its history, a rock can be lifted back to the surface o Generally accompanied by deformation, metamorphism, and magmatism (tectonics) • The Rock Cycle o Created by James Hutton to explain the recycling of older rocks into new sediment o Most rocks only go through one stage of the cycle o Stages can happen in any order 9.5 • Vesicles o Holes in volcanic rock that form when gases dissolved in magma accumulate as bubbles at or near Earth’s surface • Volcanic Breccia o Composed of angular fragments • Volcanic Glass o Forms when magma erupts on the surface and cools so quickly that crystals do not have time to form • Volcanic Ash o Some erupts vertically and settles back to Earth, cooling significantly before accumulating on the surface and consists of ash and other particles that are not strongly compressed together (tuff) o Some erupts in thick clouds of hot gas and rock fragments called pyroclastic flows that flow rapidly downhill - very hot and most parts are compacted and welded together to some extent • Porphyritic o A distinctive texture found in some igneous rocks in which larger crystals are within a finer grained matrix - indicates cooling at a lower depth and then cooling at the surface • Fine-grained o Form if the magma cooled quickly and could only grow small crystals • Medium-grained o Rocks have larger crystals that are easily visible to the unaided eye • Coarse-grained o Form at greater depths, where slow cooling allows large crystals to grow • Pegmatite o Igneous rocks containing very large crystals • Igneous rocks are organized by the size of crystals and the kinds of minerals in a rock • Felsic rock - an igneous rock with a light color and generally abundant quartz and feldspar o Granite (coarse) o Rhyolite (fine) o Pumice - volcanic rock containing many vesicles, most can float on water • Mafic rock - a generally dark-colored igneous rock containing minerals rich in magnesium and iron o Gabbro (coarse) o Basalt (fine) • Ultramafic - a composition of magma and igneous rock, generally expressed as a dark or greenish igneous rock composed chiefly of mafic minerals rich in magnesium and iron • Intermediate rocks - in between felsic and mafic rocks o Diorite (coarse) o Andesite (fine) o Tuff - volcanic rock composed of a mix of volcanic ash, pumice, crystals, and rock fragments 9.6 • A rock may be unstable because : o The minerals it contains are unstable - develops new minerals o The way the grains or layers are arranged - develops new texture • Regional metamorphism - metamorphism affecting an extensive region and related mostly to burial, heating, and deformation of rocks • Contact metamorphism - metamorphism that principally involves heating of rocks next to magma, typically without deformation • Chemical processes - o Movement of chemical elements can cause existing minerals to grow larger or form new minerals o Can grow in random orientation (common in contact metamorphism) or with preferred orientation ▪ Lineation - minerals are
More Less

Related notes for GEOG 101

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.