GEOLOGY and EARTH SCIENCE

Introduces glaciers, fossils, rock formation
and erosion, geological structures, plate
tectonics, evolution, atmospherics, astron-
omy & space science. Very rich resource
material, some at OVER 50% DISCOUNT!

SEDIMENTS, FAULTS, UNCONFORMITIES
Detailed depiction and modeling of a wide range of sedimentary and other geological structures. Makes complex formations easy to grasp. 5 prgms.100 slides,detailed texts.
EP #319X SLIDES
$149.95

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SAVE OVER $62.00 ON 5 SLIDE SET BUNDLE ORDER EP #319X...........$149.95
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GROUP REVIEW:
"These sets [Plunging Folds #313, Fault Scarps and Rifts #314, Unconformities
#315, Graded and Convoluted Bedding #319, Cross Bedding #320, Glaciers #317,
Expanding Desert #176] are an effective means of illustrating what is an especially visual
science. The topical arrangement enables teachers to build subject presentations
...effective either as an introduction...or as a summary. Thus they can be a useful
supplement to the textbook and should enhance interest and understanding..." Journal of
College Science Teaching.
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PRIMARY SEDIMENTARY STRUCTURES: GRADED & CONVOLUTED
BEDDING, BIOTURBATION, LOADING, RILL MARKS Slides order #319 .......$42.50

Examines in considerable detail many of the internal and bedding plane features
of sedimentary rocks that make possible paleoenvironmental reconstructions. Offshore
marine, beach and fluvial environments are examined. Emphasis is given to the primary
sedimentary structures developed on deep sea fan and submarine canyon deposits.
Photographs are of outcrops and environments in North Dakota, Yellowstone Plateau,
Sierra Nevada, and the California coast.

CONTENT SAMPLE: 21722 Fossil Footprints. Bioturbation features of sedimentary
rocks are structures formed by animals in sediments. They can frequently be seen on bedding
surfaces as well as inside the beds. Worm tubes, clam burrows and footprints are the most
commonly seen bioturbation structures. These are footprints of a Triassic age dinosaur about the
size of a small chicken. The animal left its footprints as indentations in the clayey sediment of a
mud flat. Sand later washed in, filling the indentations. This sand eventually hardened into solid
rock, preserving the footprints as casts. So what is seen here is the bottom bedding surface of the
sand layer that was swept in on top of the footprints of the small animal. Sandstone beds in this
position, with the casts of footprints facing up, indicate that the rocks have been overturned.
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PRIMARY SEDIMENTARY STRUCTURES: CROSS BEDDING,
RIPPLE MARKS, MUD CRACKS Slides order #320...........$42.50

Bedded rocks of aeolian, fluvial, and lagoonal origin are studied. Photogenic
exposures of cross bedded ripple marks in North Dakota and at Pebble Beach, California
are used to clarify fluvial point bar and lagoonal deposition. Mudcracks and raindrop
craters are analyzed for their environmental significance. Photographs are of exposures in
Death Valley, Zion Park, North Dakota Badlands, Colorado Plateau, Sierra Nevada, and
Pescadero Beach, CA.

CONTENT SAMPLE: 21821 Mudcrack and Raindrop Craters. Mudcracks form
when water saturated, muddy sediments dry out, compact and shrink (top). They are almost
always indicators of nonmarine deposition. In a cross sectional view, mudcracks have a
V-shaped profile. They can extend down into the fine-grained sediment as little as a few
millimeters to almost a meter. The individual polygons of dried out mud have 4, 5, 6 or 7 sides.

These features usually develop in lake basins, mud flats, playa basins, or any place
where fine-grained sediment accumulates and is periodically exposed to solar heating.

Raindrop craters (bottom) are small pits formed by the impacting of rain on a muddy
surface. Naturally, this is irrefutable evidence that the sediment surface was exposed to the
atmosphere.

If the rain falls directly on to the surface, the craters have a circular form or outline.
Craters of elliptical outline form where rain falls at an angle to the surface. Raindrop craters have a
good chance of preservation if just a few large drops impact the surface. If a downpour strikes,
there is very little chance that craters will be preserved. Raindrop craters formed in arid or
semiarid regions probably have the best chance of preservation.

Shown here is a slab of clayey sandstone. The raindrop craters near the paper clip have
a slightly elliptical shape indicating that the rain fell at an angle to the surface.

Many Precambrian rocks of the Rocky Mountains, although devoid of fossils, still tell us a
lot about their environments of deposition because of the beautifully preserved mudcracks and
raindrop imprints on bedding planes.
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GEOLOGIC STRUCTURES:
THE DEPICTION OF PLUNGING FOLDS Slides order #313..........$42.50

Structure selections, block diagrams and colored clay models are presented to
clarify three-dimensional concepts such as dip and strike, plunge of folds, law of V's, and
fold patterns. Photographs of eroded clay model folds provide a clearer approach to the
teaching of fold patterns and the law of V's. A plunging fold, the Moss Beach syncline,
considered by many the finest example of a plunging fold along the Pacific Coast, is
examined in detail.

CONTENT SAMPLE: 20979 Clay Model Folds. The various rock patterns made by
folded sedimentary rocks are best understood by constructing clay model anticlines and
synclines. The clay models should be built from colored clays that will not harden when exposed
to the air. Knead the clay until it is soft enough to be rolled flat by a rolling pin. Several clay layers
are rolled flat and then stacked one atop another. Then the sides of the model are trimmed to
make a rectangular block. In the model shown here, two anticlines and one syncline were made
by pressing the clay down over a wooden dowel. The black tape indicates the axes of the folds.
The white N indicates that north is toward the back of the block.
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GEOLOGIC STRUCTURES: FAULT SCARPS AND RIFTS Slides order #314............$42.50

Three-dimensional block diagrams are used to clarify which is the hangingwall
and which is the footwall of a tectonic fault. The classification of dip-slip and strike-slip
faults is shown. The graben and horst structure of the southwest Great Basin is examined
in detail. Depicts the Sierra fault scarp with its associated volcanic and glacial features,
geologic hazards along the San Andreas fault, as well as tectonic creep along the
Hayward fault.

CONTENT SAMPLE: 20997 Right Lateral Strike Slip Fault. In strike slip faulting, the
movement of rock along the fault plane is horizontal and parallel to the strike of the fault. There
are two kinds of strike slip faults: right lateral and left lateral. This diagram shows a right lateral
fault.

Right lateral faulting is best understood in terms of an observer standing on one block
looking across the fault plane at the displaced block. If the displaced feature such as a railroad
track, river channel, line of trees, etc., has been moved to the right, then we term the fault a right
lateral fault.

The amount of displacement that can take place along a strike slip fault can vary along
the strike of the fault. For example, during the 1906 San Francisco earthquake the maximum
displacement was about 21 feet north of San Francisco near Point Reyes, California. South of
San Francisco the displacement decreased to only a few feet in Santa Clara County.

Repeated movements along a fault like this can result in mountain ranges and rock units
being displaced tens or even hundreds of miles. Many geologists believe that the amount of right
lateral displacement along the San Andreas fault of California can be measured in hundreds of
miles.

Because the shattered rock along large strike slip faults is so easily eroded, streams and
rivers carve linear valleys (rift zones) along the trend of the fault. Landslides, springs, displaced
stream channels, and slickensided bedrock surfaces also characterize these fault zones.
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GEOLOGIC STRUCTURES: UNCONFORMITIES Slides order #315 ..........$42.50

These pauses or interruptions in the sedimentary record of a region are examined
in detail. Diagrams are used to explain how angular unconformities, nonconformities and
disconformities develop. Various unconformities and their significance in the geological
evolution of the U.S. West are shown.

CONTENT SAMPLE: 21408 Angular Unconformity-Nonconformity. These four
cross sections show the successive stages in the development of both an angular unconformity
and a nonconformity. The upper left cross section shows a series of beds that have been
deposited on the sea floor. In the upper right section the rocks have been uplifted and folded
by powerful, laterally-oriented, compressional stress. As soon as the rocks are uplifted above sea
level they are acted on by the agents of erosion, especially rivers and streams. In the lower left
diagram we see a cross section depicting the region after it has experienced a long interval of
erosion. The orange color represents a large mass of plutonic igneous magma that is intruding the
folded sedimentary rocks. This intrusive rock eventually crystallizes and is partially uncovered by
erosion.

The cross section in the lower right shows the region after an ocean has inundated it
again. New, younger beds of sedimentary rock are washed in on top of the truncated and eroded
edges of the sedimentary rocks and the intrusive rock. The surface that separates the folded older
sedimentary rocks from the younger horizontal strata is called an angular unconformity. The
surface that separates the older solid plutonic igneous rock from the overlying horizontal strata is
known as a nonconformity. Both unconformities represent a buried erosional surface.

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RELATED PROGRAM WORTH NOTING
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THE EXPANDING DESERT Order #176..........$42.50

Introduces and summarizes the causes and results of the expansion of desert
areas worldwide, with special reference to the Sahal. Discusses man's role in the spread
of deserts and what can be done to halt it. Pictures from Africa and the U.S. illustrate
deserts, overgrazing, refugees, irrigation and water utilization. 20 slides and guide.

CONTENT SAMPLE: 21678 The world's largest, most famous desert is the Sahara. The
name is Arabic for brown and empty and when properly pronounced, the "h" sound suggests that
the speaker has a dry, sore throat, as if he had been exposed to the desert too long. The Arab
uses the word not to name any particular desert, but all deserts, or more accurately, all dry,
barren lands, whether or not sand is prominent.

The Sahara is immense, stretching for 5,149 km (3,200 miles) across North Africa, an
area practically the size of all 50 United States. To the north it extends to the Mediterranean
Sea, and includes mountain areas. Southward it runs into the savannas and then into the
tropical jungles. Although the Sahara has a population of more than three million, it seems to
swallow them up, dwarfing people and their habitations as the ocean dwarfs a ship. Considered
a sea, the Sahara's southern fringe is called the Sahel, which is Arabic for shore or edge. This
Sahelian area caught the attention of the world in the early 1970's when a severe drought caused
mass hunger, starvation and death.

REVIEWS: "... an effective means of illustrating what is an especially visual science.
The topical arrangement enables teachers to build subject presentations...effective either as an
introduction...or as a summary. Thus they can be a useful supplement to the textbook and
should enhance interest and understanding..." Journal of College Science Teaching.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~1874-082~ Canyonlands. photo by Charles R. Belinky, Ph.D.

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