A Tour of Geomorphology
Mentor Answer Key
Here is a key that you can use to assess student responses. These sections have
been copies directly from the websites. Student answers should be written in their
own words and should not be copied and pasted. This key will help you to judge is
student comprehension is on target and if student work is authentic.
1. Provide an overview of geomorphology and describe topics a geomorphologist
would study.
There is a lot of information in this site, so student answers will vary. You may
want to read through the material to assure that students are generating their
own work.
2. Describe three geomorphologic studies that have been conducted
Student answers will vary, but all should be associated with changes to Earth’s
surface.
3. Click on the geologic map and explain what a geologic map is.
This component of the tapestry is simplified from the geologic map of King and Beikman
(1974). Rocks contain information essential to an intelligent understanding of the Earth
and its long natural history. Geologists determine the location, geographic extent, ages
and physical and chemical characteristics of rocks and unconsolidated (loose) materials.
To express these attributes geologists have developed a unique method of portrayal,
the geologic map, which has the following properties:
It recognizes similarities and differences among materials that make up the Earth's
crust and classifies them by type of rock or surficial deposit;
It ascribes Earth materials to a specific environment or mode of origin- for example,
volcano, river deposit, windblown dune, limestone reef, alteration at depth by
heat or pressure;
It identifies rock formations of distinctive materials and ages that are the threedimensional building blocks of the Earth's crust; it further shows the relative
position of one formation to another at the Earth's surface;
It arranges rock formations of different ages into a time sequence from which
the geologic history of the planet can be deciphered.
4. Explain what you learned by watching the flash video of “The Two Maps” (Click
on the “Watch the Maps Merge” button).
Through computer processing and enhancement, we have brought together two
existing images of the Nation's lower 48 states into a single digital tapestry. Woven
into the fabric of this new map are data from previous U.S. Geological Survey (USGS)
maps that depict the topography and geology of the United States. The resulting
composite is the most detailed and accurate portrait of the U.S. land surface and the
ages of its underlying rock formations yet displayed in the same image. The new
map resembles traditional 3-D perspective drawings of landscapes with the addition
of a fourth dimension, geologic time, which is shown in color. In mutually enhancing
the landscape and its underlying temporal structure, this digital tapestry outlines the
geologic story of continental collision and break-up, mountain-building, river erosion
and deposition, ice-cap glaciation, volcanism, and other events and processes that
have shaped the region over the last 2.6 billion years.
5. Click on the topographic map and explain what a topographic map is.
This component of the tapestry is the digital shaded-relief image, created by Thelin and
Pike (1991), that shows the shape of the land surface by variations in brightness. The
degree of light and dark artificially mimics the intensity of the Sun's light on different
types of topography. This technique, called chiaroscuro, dates back some 400 years to
sketches of the Tuscan landscape by Leonardo da Vinci. Because manual (artistic)
portrayals of terrain can practicably show only small areas both accurately and in detail,
the technique has been automated by the computer to cover large regions. The
resulting digital shaded-relief map of the lower 48 states succeeded the unique, if less
accurate, hand-drawn landform map by master cartographer Erwin Raisz.
Landscape features contain many of the clues needed to understand the Earth and the
agents that have shaped it. Finding and decoding these clues enables scientists to learn
more about natural hazards, the events of Earth history, and resources of land, water,
energy, and minerals. Many methods of landscape portrayal are used to view surface
features, but shaded-relief imaging by computer is unique in the following respects:
It provides fine-scale detail over a wide area, a combination not possible in other
techniques of illustration;
It shows terrain accurately and in its true complexity, two properties commonly lost in
sketches and diagrams of large areas;
Unlike mosaics of aerial photos and radar images, the view -- limited only by extent of
the digital data set -- is continuous across the country;
Relief shading is free of distortion and the vegetation and cultural features that
conceal topographic form on satellite images.
4. Click on the “Description of Features” link and select #14 and explain what you are
looking at.
The Fall Line is a low east-facing cliff paralleling the Atlantic coastline from New Jersey
to the Carolinas. It separates hard Paleozoic metamorphic rocks of the Appalachian
Piedmont to the west from the softer, gently dipping Mesozoic and Tertiary sedimentary
rocks of the Coastal Plain. This erosional scarp, the site of many waterfalls, hosted
flume- and water-wheel-powered industries in colonial times and thus helped
determine the location of such major cities as Philadelphia, Baltimore, Washington, and
Richmond.
5. Click on the “Metamorphic Rocks” link. What did you learn about metamorphic rock
layers? Where are these rock layers found?
Sometimes it is difficult to tell how old a rock is. This is especially true of metamorphic
rocks. Metamorphic rocks are rocks that have undergone a change, usually due to high
temperatures and/or pressures. The heat and pressure that they have been subjected to
often "resets" their geologic clocks to the time of their metamorphism.
These rock layers are found in a south-west to north-east band along the east coast of
the United States.
6. Click on the link “about the Cambrian and Ordivician Periods”. What did you learn
about these rock layers? Where are they found?
The rocks highlighted here are some of the oldest in the United States. They formed in
the Cambrian Period, between 560 and 504 million years ago, and the Ordovician
Period, between 504 and 438 million years ago. The Cambrian Period is the earliest
division of the Paleozoic Era, followed by the Ordovician period. During the Cambrian,
life began to bloom in the Earth's oceans. By the Ordovician, marine life was very
diverse, with creatures like primitive fish, corals, and trilobites.
These rock layers are found throughout the United States, but are concentrated in a
band running south-west to north-east along the eastern coast of the United States.
7. Click on the link “about the Upper Tertiary Period”. What did you learn about these
rock layers? Where are they found?
The rocks highlighted here are some of the youngest in the United States. They
formed in the late Tertiary Period, between 38 and 1.6 million years ago. The
Tertiary Period is subdivided into epochs. The youngest Tertiary epochs, the
Miocene, Pliocene, and Oligocene are shown here. During this time, sediments
eroded from the uplifting Rocky Mountains were being deposited in huge alluvial
fans that formed the Great Plains. In the eastern U.S., sediments were also being
deposited, forming the Coastal Plain. In the west, subduction led to the formation of
a chain of volcanic mountains called the Cascade Range.
They are found at several locations out west and in a narrow band along the
coastline from Texas to New York.