6.6: Review and Additional Resources

Summary

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". 

Figure \(\PageIndex{1}\): A wide-angle view of the Grand Canyon showing distinct horizontal sedimentary rock layers on the canyon walls and the Colorado River. (CC BY-ND 4.0; Courtesy Mrinmoy Ghosh).

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

Citations

• OpenAI. (2026). ChatGPT (GPT-4o version) [Large language model]. https://chatgpt.com
• Google. (2026). Gemini (Gemini 1.5 Pro version) [Large language model]. google.com
• King, H. M. (n.d.). Pumice: Igneous rock - pictures, definition & uses. Geology.com.
• Leong, G. C. (1983). Certificate in physical and human geography (3rd ed.). Oxford University Press.
• National Park Service. (n.d.). How fossils form. U.S. Department of the Interior.
• National Park Service. (n.d.). Natural Bridge. U.S. Department of the Interior.
• Ritter, M. E. (2020). The physical environment: An introduction to physical geography. (L. Pitts, Ed.).
• U.S. Geological Survey. (n.d.). What are sedimentary rocks? U.S. Department of the Interior.

Multimedia

• The Physical Environment: Watch National Geographic’s Fossils 101 to learn how fossils form and how they help scientists understand Earth’s history. This video introduces the fossilization process and explains how fossils provide evidence about ancient organisms, past environments, and geologic change over time.
• The Physical Environment: Watch SciShow’s What's actually inside the Earth's core? to learn how scientists study Earth’s interior and what evidence helps them understand the core. This video connects planetary structure to seismic data, temperature, and pressure.
• The Physical Environment: Watch TED-Ed’s Volcanic eruption explained to learn how volcanic eruptions happen and why they vary in intensity. This video connects magma, pressure, and tectonic setting to volcanic hazards and landscape change.

Readings

• The Physical Environment: Read Mechanisms for plate motion in Introduction to Oceanography to learn how tectonic plates move and what forces help drive that movement. This resource helps students connect mantle processes, ridge push, slab pull, and plate interactions to the larger theory of plate tectonics.
• Physical Geography Today: Explore BBC News’ In depth: Asia quake disaster to learn how a major earthquake and tsunami affected coastal environments and human communities. This resource connects seismic activity, coastal hazards, and disaster impacts to real-world physical geography.
• Physical Geography Today: Explore the U.S. Geological Survey’s Earthquake Hazards Program to learn how scientists monitor earthquakes, map seismic activity, and share hazard information with the public. This resource helps students connect plate tectonics, seismic risk, hazard monitoring, and public safety to real-world physical geography.