14.6: Review and Additional Resources

Review

Figure \(\PageIndex{1}\)

Review and assess your learning. Start with the "Important Terms and Concepts" to ensure you know the terminology related to the topic of the chapter and concepts discussed. Move on to the "Review Questions" to answer critical thinking questions about concepts and processes discussed in the chapter. Finally, test your overall understanding by taking the "Self-assessment quiz".

Important Terms and Concepts

• compressional wave

  generate a back-and-forth motion parallel to the direction of travel

• shear wave

  move up-and-down perpendicular to the direction of wave transmission

• crust

  outer brittle shell of the Earth; forms the "skin" of the lithosphere. The crust is primarily composed of silicate rocks and ranging in thickness of about 5 to 70 km

• sima

  basal zone of oceanic crust; primarily composed of a heavy, dark group of basaltic rocks

• sial

  less dense continental crust; predominate elements are silicon and aluminum

• lithosphere

  rigid cool layer composed of the crust and the uppermost mantle

• asthenosphere

  the least rigid portion of the mantle. It is a soft, easily deformed layer that is susceptible to slow convection caused by pockets of increased heat from the decay of radioactive elements

• mesosphere

  lies between the asthenosphere and core where the pressures are so great the mantle is solid

• core

  molten outer and rigid inner layers

• mantle

  over 2900 km thick (1801 mi) and comprises 80% of the Earth's total volume; mainly composed of a dark, dense ultramafic rock called peridotite (rich in iron and magnesium)

• endogenic force

  forces that are are driven by the Earth's vast heat engine

• exogenic force

  processes acting at the surface of the earth and primarily driven by solar energy

• relief

   the difference in elevation between two points

• first order relief feature

  the tectonic plates

• second order relief feature

   the result of plate collision or divergence

• third order relief feature

  created by erosion and deposition of the surface as opposed to the movement of tectonic plates. Individual landforms are considered third order relief features

• mineral

  a naturally occurring inorganic substance with a unique crystal structure

• silicate

  a combination of silicon, oxygen, and another element; see Table 14.4.1

• oxide

  see Table 14.4.1

• sulfide

  see Table 14.4.1

• carbonate

  see Table 14.4.1

• rock cycle

  represents the alteration of rock-forming minerals above and below the Earth's surface

• rock

  assemblages of minerals

• magma

   molten rock material

• sediment

   fragments of weathered rock and the precursor for sedimentary rock

• igneous rock

  cooled/crystallized magma or lava

• sedimentary rock

  formed by compaction and cementation of sediments

• metamorphic rock

  formed by the alteration of pre-existing rocks from exposure to heat and pressure while remaining in a solid form

• clastic sedimentary rock

  form from the compaction of rock fragments

• chemically precipitated sedimentary rock

  form by the precipitation of elements

• country rock

  the pre-existing rock that insulates the magma that has intruded as it cools

• sill

  feature created when magma intrudes between the layers of rock and solidifies

• dike

  created when magma cools in near vertical fractures

• laccolith

  created when the magma solidifies as a pocket of igneous rock that warps the overlying rock

• batholith

  a huge intrusive igneous rock mass or pluton that when uncovered creates topographic highs in mountainous regions.

• pluton

  rock mass in which magma has intruded and solidified

• vesicles

  small holes; void spaces left by escaping gasses

• stratum

  individual layer of sedimentary rock

• bedding plane

  separation between each bed; signifies a cessation of deposition at that location for a period of time

• lithostatic pressure

   the confining pressure created by the material that sits above a particular location; equal in all directions and compresses the volume of rock into a denser material

• directed pressure

  flattens and lengthens the rock in the direction of greatest pressure; affects the shape and arrangement the minerals

• burial metamorphism

  occurs in deep basins where sediments or sedimentary rocks have accumulated. At a depth of about 10 kilometers, the confining pressure of the overlying material combined with geothermal heat is great enough to metamorphose rocks.

• contact metamorphism

  occurs at shallower levels of the crust, where the pressure is relatively low. At those shallow depths, the stresses characteristic of orogenic belts are generally small or absent thus producing metamorphic rocks that lack foliation

• regional metamorphism

  occurs over broad areas of the crust; occurs in a linear belt in the plate overriding the subducting one due to increasing temperature and pressure as a result of compression, thrusting, folding, and intrusion of magmas from below.

• dynamothermal metamorphism

  occurs in areas that have undergone deformation during mountain building that have since been eroded to expose the metamorphic rocks. It is caused by the differential stress resulting from plate subduction or collision along plate boundaries

• foliated metamorphic rock

  minerals in distinct bands

• nonfoliated metamorphic rock

  lack the banding of minerals

Review Questions \(\PageIndex{1}\)

Compare and contrast compressional and shear waves.

Answer

Compressional (P) waves generate a back-and-forth motion parallel to the direction of travel. Shear (S) waves move up-and-down perpendicular to the direction of wave transmission. Shear waves do not penetrate molten masses and when they encounter a boundary between two rock types of differing densities, a portion of the wave travels along the boundary while another part returns to the surface.

Compare and contrast the sima and sial.

Answer

Sima refers to silica and magnesium, two important elements of the rocks forming the ocean basin like basalt. Sial refers to silica and aluminum, two important elements that comprise the rocks of the continents like granite.

Briefly describe the layers of the mantle.

Answer

The uppermost part of the mantle includes part of the lithosphere. Below the lithosphere is the asthenosphere, the least rigid portion of the mantle. Finally the mesosphere is the bottom most portion comprised of solid rock.

Describe the basic structure of the Earth's core.

Answer

The core is divided into the inner and outer cores. The inner core is made of solid iron and nickel. The outer core is thought to be molten iron.

Compare and contrast endogenic and exogenic forces. Give examples.

Answer

Endogenic forces are those driven by Earth's "heat engine" like volcanoes and earthquakes. Exogenic forces are driven by solar radiation like wind and water erosion.

Compare and contrast first, second, and third order relief features. Give an example for each.

Answer

First order relief features are the tectonic plates. Second order relief features are formed by plate interaction, e.g. mountain systems, ocean trenches. Third order relief features are produced by the erosion or deposition e.g., sand dunes, mountain peak.

What is a mineral and how is it different from a rock?

Answer

A mineral is an inorganic substance having a unique crystalline structure while a rock is a combination of minerals.

What is the rock cycle?

Answer

It is a model of the interrelationships between the three types of rocks and how they form.

Compare and contrast the physical features of intrusive and extrusive igneous rocks.

Answer

Extrusive igneous rock has smaller mineral grains and thus finer texture than intrusive igneous rocks.

Briefly describe how a sill, dike, batholith, and laccolith form.

Answer

Sill - magma intrudes between layers of host rock and solidifies. Dike - magma solidifies in a near vertical fracture. Batholith - huge subterranean mass of igneous rock. Laccolith - magma intrudes between layers of host rock, then warp the overlying layers.

Compare and contrast the various types of sedimentary rocks. Give examples.

Answer

Clastic sedimentary - formed from fragments, example = sandstone. Chemical (nonclastic) - formed from a precipitate. Example = limestone. Biologic sedimentary - Compaction of animal remains. Example = coal.

Compare and contrast the various types of metamorphism.

Answer

Contact metamorphism occurs along contact zones between pre-existing rock and a cooling pluton.

Regional metamorphism occurs over broad areas of the crust. There are two basic kinds of regional metamorphism: dynamothermal metamorphism - deformation during mountain building. burial metamorphism - occurs in deep basins where sediments or sedimentary rocks have accumulated.

What is the fundamental difference between foliated and nonfoliated metamorphic rocks.

Answer

Foliated metamorphic rocks display banding of minerals, nonfoliated do not.

Self-Assessment Quiz \(\PageIndex{1}\)

1. Waves of seismic energy propagated as a back-and-forth motion are called
   1. compressional waves
   2. shear waves
   3. surface waves
   4. none of the above
2. The sima is primarily composed of
   1. granitic-type rocks
   2. basaltic-type rocks
   3. limestone-like rocks
   4. none of the above
3. Which of the following layers are, we think, composed of solid nickel and iron?
   1. The asthenosphere
   2. The lithosphere
   3. The outer core
   4. The inner core
4. Which of the following is created by endogenic forces?
   1. Glacial erosion
   2. Water erosion
   3. Wind erosion
   4. Faulting
5. The Himalaya Mountains are a _____ relief feature of the Earth.
   1. first
   2. second
   3. third
   4. fourth
6. The most abundant mineral family is the
   1. silicates
   2. oxides
   3. sulfides
   4. carbonates
7. Metamorphic rocks form from
   1. sedimentary rocks
   2. igneous rocks
   3. other metamorphic rocks
   4. all the above
8. An intrusive igneous rock body formed by the cooling of magma in a nearly vertical fracture is called a
   1. dike
   2. sill
   3. laccolith
   4. batholith
9. Granite is
   1. an extrusive igneous rock
   2. a clastic sedimentary rock
   3. a nonfoliated metamorphic rock
   4. none of the above
10. Quartzite is
    1. an extrusive igneous rock
    2. a clastic sedimentary rock
    3. a nonfoliated metamorphic rock
    4. none of the above

Answer

1. A
2. B
3. D
4. D
5. B
6. A
7. D
8. A
9. D
10. C

Additional Resources

Use these resources to further explore the world of geography

Focus on The Physical Environment: "Earth's Core" Naked Science

Connections: "Evolution of Landscape Change along Clear Creek, Colorado" USGS. A look at the effects of urbanization, aggregate mining and reclamation.

Multimedia

"The Chemistry of Earth" The World of Chemistry video series (Annenberg/CPB) "Silicon, a cornerstone of the high-tech industry, is one of the elements of the Earth highlighted in this program." Additional information about Earth structure and mineral formation is included. Go to the The World of Chemistry site and scroll to "The Chemistry of Earth". One-time, free registration may be required to view film.

"Intrusive Igneous Rocks" Earth Revealed video series (Annenberg/CPB)
Most magma does not extrude onto Earth’s surface but cools slowly deep inside Earth. This magma seeps into crevices in existing rock to form intrusive igneous rocks. Experts provide a graphic illustration of this process and explain the types and textures of rocks such as granite, obsidian, and quartz. Once again, plate tectonics is shown to be involved in the process. Go to the Earth Revealed site and scroll to "Intrusive Igneous Rocks". One-time, free registration may be required to view film.

"Metamorphic Rocks" Earth Revealed video series (Annenberg/CPB) "The weight of a mountain creates enough pressure to recrystallize rock, thus creating metamorphic rocks. This program outlines the recrystallization process and the types of rock it can create — from claystone and slate to schist and garnet-bearing gneiss. The relationship of metamorphic rock to plate tectonics is also covered." Go to the Earth Revealed site and scroll to "Metamorphic Rocks". One-time, free registration may be required to view film.

"Sedimentary Rocks": The Key to Past Environments Earth Revealed video series (Annenberg/CPB) This program returns to the Grand Canyon: its exposed layers of sedimentary rock allow scientists to peer into the geologic past. The movement of sediment and its deposition are covered, and the processes of lithification, compaction, and cementation that produce sedimentary rocks are explained. Organic components of rock are also discussed. Go to the Earth Revealed site and scroll to "Sedimentary Rocks: The Key to Past Environments". One-time, free registration may be required to view film.

Readings

Uncovering Hidden Hazards in the Mississippi Valley (USGS)

The Mississippi Valley-"Whole Lotta Shakin' Goin' On" (USGS)