Lesson Plan

Physical Features of the Earth

Desert sandstones and snow-capped mountains

NPS photo by Neal Herbert

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Grade Level:
Fifth Grade
Subject:
Earth Science, Geology
Duration:
Field trip stations are 30 minutes each. Pre and post trip lessons are 45 minutes
Setting:
in the park
National/State Standards:
Utah State Standard Core Curriculum Topic, Standard Two: Students will understand that volcanoes, earthquakes, uplift, weathering, and erosion shape Earth's surface.
Keywords:
erosion, weathering, earthquakes, uplift, arch formation, fossil, fault, deposition, geologic layers

Overview

Students assemble jigsaw puzzles in the classroom informing them about the different types of rock and the rock cycle. At a field trip site, students examine a limestone layer to find fossils and make clay models to reenact movement along a local fault. They explore and model the formation of arches, and learn the names and deposition histories of the rock layers surrounding them. Back in the classroom, a mapping activity demonstrates what causes many earthquakes: plate tectonics.

Objective(s)

PRE-TRIP ACTIVITY
A Piece at a Time

a. Name the three main types of rocks.
b. Describe the processes that created four diff erent landforms.

INTRODUCTORY ACTIVITY
Rock and Roll

a. Name sand grains as the main component of sandstone.

STATION #1
Fossil Frolic

a. Name three types of marine fossils.
b. Describe the environment in which the limestone was deposited.

STATION #2
Who’s Fault Is It Anyway?

a. Define a geologic fault.
b. Describe how the rock layers moved along the Moab fault.

STATION #3
Falling Arches

a. Name three types of arches.
b. Describe two weathering processes involved in arch formation.

STATION #4
Picture This

a. List three of the rock layers in Arches National Park.
b. Describe three environments in which the rock layers were deposited.

POST-TRIP ACTIVITY
Plates on the Go

a. Explain why earthquakes are most common along plate boundaries.
b. Explain how plate tectonics creates new igneous and metamorphic rocks.


 

Background

The rock layers and fault exposed at the entrance to Arches National Park are of textbook quality. The layers are easy to see; they have different colors as well as different compositions.

By looking at the rocks close-up, we learn about the ancient environments in which the sediments of the rock layers were deposited. Most mudstones and siltstones formed in low-gradient streams or tidal-fl at environments. Some sandstones were deposited in steeper streams or on beaches. Sandstones made up of very rounded sand grains that are all the same size (well-rounded and well-sorted, in geological terms) indicate aeolian or windblown deposition in a relatively dry environment. Limestones usually indicate a marine environment, and many contain fossils. (A few thin limestone layers in the Moab area were deposited in freshwater lakes.)

Any plant or animal that dies on earth can be fossilized if the conditions are correct. In order for a creature, or evidence of a creature, to be preserved as a fossil, the creature cannot be broken down or disintegrated. Many fossils are formed at the bottom of oceans, where deposition is continuously occurring and dead organisms are quickly buried. This, and the fact that many marine creatures have hard shells that don't decompose easily, is why most fossils are of marine organisms. Fossils of land-dwelling Delicate Arch creatures are less common. The Honaker Trail Formation, found in the bottom of Bloody Mary Wash, contains an abundance of fossils. This limestone layer was deposited in an off shore marine environment about 300 million years ago. There are fossils of crinoids, brachiopods, bryozoans, horn corals, and occasional clams, snails, and trilobites.

A geologic fault is a break or fracture in the rock, along which there is displacement of the strata. Most faults form during earthquakes or volcanic activity associated with the shifting of tectonic plates. In southeastern Utah, however, much faulting is associated with an unusual phenomenon, the movement of underground salt layers. Faults are commonly buried by sediment and difficult to see, but the Moab fault is spectacularly exposed at the field trip site. The Honaker Trail Limestone has been shifted 2,500 feet upward on the west side of the fault, past seven other rock layers. It is now on the same level as the Entrada Sandstone (Dewey Bridge Member) east of the fault.

Arches National Park's erosional landscape of valleys, towers, fins, canyons, pinnacles, and arches began to form about 10 million years ago. That's relatively young in geologic terms; the rock layers in the park were deposited roughly 300 million to 150 million years ago.

Based on the defiition of an arch as an opening at least three feet in one direction, there are over 2,000 named arches in Arches National Park, most within the Entrada Formation. Water is the main culprit in arch formation. Rainwater is usually slightly acidic, which weakens the cement between grains in the sandstone. The process of frost wedging involves water freezing (expanding) and thawing (contracting) in pores and cracks. This process is key in breaking apart sand grains, especially because of the large temperature fluctuations of the high desert climate. In addition to water, wind and gravity aid in the process of erosion by removing the weathered parts of rocks. Arches can be classified by their shapes; categories include free-standing arches, cliff -wall arches, and jughandle arches. Natural bridges, unlike arches, are formed by flowing streams.

Plate tectonics is the driving force for faulting, earthquakes, and the melting and pressure that recycles rocks into new igneous and metamorphic rocks. The Earth has several layers: crust, mantle, outer core and inner core. The lithosphere, which is the crust plus the upper part of the mantle, is broken up into different pieces called plates that move around in different directions on the Earth's surface. There are three basic types of boundaries between these plates. Convergent boundaries are where plates crash together. In this case, one plate usually descends beneath the other. Plates made up of oceanic crust are thicker and heavier, so they sink below the lighter, thinner continental plates. Here, friction causes massive pressure, earthquakes, faulting, and mountain building. The descending plate melts, only to rise up as a liquid magma and form volcanoes along the edge of the overriding plate. In a few cases, when both of the lithospheric plates are made up of continental crust, neither plate descends, and the earthquakes and faulting create massive mountains such as the Himalaya. Divergent plate boundaries or rifts, where plates spread apart, are usually in the middle of oceans. Basaltic lavas flow from these boundaries, creating new crust. Transform plate boundaries, where plates slide by each other, are illustrated by the San Andreas fault in California.

Procedure

Park Connections

Bloody Mary Wash, immediately west of Arches Visitor Center parking lot, is the ideal location for these activities. This site is unique in having a fossiliferous limestone in the wash bottom and a beautifully exposed geologic fault. All stations could be adapted for various geologic settings in southeastern Utah, but perhaps nowhere would have all the combined features of this site.

Extensions

STATION #1
Fossil Frolic

Have students name three kinds of fossil creatures and tell something about how each lived. Have students describe the environment in which these creatures lived.

STATION #2
Who's Fault Is It Anyway?

Assign students to research and make models of different types of geologic faults. Insert fault definition cards and fault cross section from current guide

STATION #4
Picture This

Have students draw a profile of the wall east of the visitor center, labeling the depositional environment of each layer: stream, sand dune, or tidal fl at. (There are no layers representing ocean environments east of the Moab fault.)

Additional Resources

Baars, D. L. (1993). Canyonlands country: Geology of Canyonlands and Arches National Parks. Salt Lake City, UT: University of Utah Press.

Brady, I. (1998). The redrock canyon explorer. Talent, OR: Nature Works.

Chesterman, C.W. (1978). The Audubon Society field guide to North American rocks and minerals. New York, NY: Alfred Knopf.

Cuff , K. (1995). Stories in stone: Teacher's guide, grades 4-9. GEMS Series. Berkeley, CA: Lawrence Hall of Science, University of
California.

Doelling, H. H. (1985). Geology of Arches National Park. Utah Geological and Mineral Survey Map 74, and accompanying booklet, 15p.

Fluegelman, A., (ed.). (1976). The new games book. Garden City, NY: Headlands Press, Doubleday.

Geology: The active earth. (1988). Ranger Rick's NatureScope Washington, DC: National Wildlife Federation.

Rhodes, F.H., Zim, H.S. & Shaff er, P.R. (1962). Fossils: A guide to prehistoric life. Golden Guide. New York, NY: Golden Press.

Stevens, D. J., & McCarrick, J. E. (1988). The arches of Arches National Park, A comprehensive study. Orem, Utah: Mainstay Publishing.

Thompson, I. The Audubon Society field guide to North American fossils. New York, NY: Alfred Knopf.

Williams, D. (1997). Geology: Arches National Park. Moab, UT: Canyonlands Natural History Association. Brochure.

Williams, D. (2000). A naturalist's guide to canyon country. Helena, MT: Falcon Publishing.

Vocabulary

Earthquakes, erode, erosion, faults, uplift, volcanoes, weathering, buttes, arches, glaciers,
geological, deposition

Last updated: December 22, 2017