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!

SUBMARINE LAND FORMATIONS
Underwater land formations, how they occured and the techniques by which they are studied. Many graphics and multi- ple images. 4 pgms. 55 slides and texts.
EPSS-0755X SLIDES
$119.95

****************************************************************************************************************
SAVE OVER $34.00 ON 4 SLIDE SET BUNDLE ORDER EP #SS-0755X.....$119.95
****************************************************************************************************************

SUBMARINE TOPOGRAPHY Slides order #SS-0750S.........$42.50

After outlining the earliest methods of depth determination, this program
introduces the most modern methods of studying submarine topography. Shows how the
composition of the ocean basins is pursued for economic gain as well as for scientific
enlightenment. Physiographic details of the Atlantic Basin, the Pacific Basin, the Indian,
the Arctic, and Antarctic are differentiated. 15 frames, cassette and guide. (Filmstrip
order SS-0750F........$15.00.)

CONTENT SAMPLE: 1. It has been said that we know more about the topography of
the dark side of the moon than we do about the ocean floor. An average of 4,000 m of seawater
conceals the relief and features of the ocean basins from our view. Absorption and scattering of
light obscures the bottoms of even shallow coastal waters.

Up until 50 years ago water depth was determined by line sounding. A weight was
lowered from the side of a vessel by a sounding line; when the bottom was felt, the depth was
indicated by the length of line that had been played out.

Mariners have sounded river and coastal waters since ancient times as an aid to navi-
gation. The first recorded sounding of the open ocean was made by Magellan in 1521 during
his circumnavigation of the globe. Magellan lowered about 400 m (1,200 ft) of rope into the
Pacific without striking bottom.

The Challenger Expedition (l872-1876) made the first systematic attempt to chart the
basins of the world ocean. The Challenger employed a steam-powered winch to lower and recover
kilometers of hemp sounding line. The deepest sounding made on the expedition was 26,850 ft.
off the Marianas. Subsequent oceanographic expeditions used steel wire as sounding line;
Challenger had unsuccessfully experimented with piano wire, which kinked badly.

During the next half century the principal topographical features of the ocean basins were
revealed by wire-line soundings, though the method was still cumbersome and inexact A
vessel had to be held stationary during the hours it took to lower and recover a soundings line in
deep water. At great depths the weight of the sounding line would exceed that of the end weight,
making it difficult to determine when the bottom was reached. Finally, the assumption that a
sounding line drops perpendicular to the bottom seldom holds true; drifting of the vessel and
subsurface currents tend to displace the sounding line obliquely. Overestimates of the actual
depth consequently result from measuring the actual length of line played out.

Modern oceanographic vessels still carry huge spools of multistrand steel wire, as shown
here, and heavy winches for lowering apparatus to the ocean bottom, but depth measurements
are no longer determined by line sounding.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

DEEP-SEA SEDIMENTS Slides order SS 0755S.........$34.95

The importance of ocean floor sediments as a record of the earth's history is
discussed. Also relates ocean floor sediments to increased understanding of continental
drift and the periodic onset of ice ages. Presents an overview of the methods of data
collection and analysis. 10 frames, cassette and guide. (Filmstrip order SS-0755F
.......$15.00.)

CONTENT SAMPLE: 1. The sediments that cover the ocean floor provide an
invaluable record of the earth’s history. By studying this record we can better understand such
phenomena as continental drift and the periodic onset of ice ages. In addition, a knowledge of
sediments and the processes of sedimentation have practical applications for deep-sea mining,
the laying of submarine communication cables, and the disposal of radioactive and other toxic
wastes on the ocean floor.

Such studies are time consuming and expensive because the bottom of the ocean is
relatively inaccessible to observation. Sixty percent of the earth’s surface is covered by more
than 1,000 m of seawater, and more typical depths range from 4 to 5 km. Just mapping the
profiles of submarine topography was a formidable task before the invention of echo sounding
devices in the early twentieth century. Recovery of bottom samples was sometimes achieved by
coating the lead sounding weight with tallow (animal fat). When the weight hit the bottom
surface, sediments would adhere to the tallow and could then be retrieved with the sounding
lines. Other methods included dredging sediments from the bottom or sampling the upper
sediments with a grab sampler. All of these methods recovered material from the water/
sediment interface, or slightly below it, in a rather qualitative manner--the recovered samples
were mixed together with no retention of horizontal profiles.

In 1945 the Swedish oceanographer Borje Kullenberg developed a piston corer that could
recover a horizontal profile of bottom sediments up to 20 m (65 ft.) deep. The operation of such a
free-fall corer in the deep sea is illustrated in this slide.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SUBMARINE CANYONS AND DEEP SEA FANS Order #322 ........$42.50

An introduction to the formation of submarine canyons and deep sea fans. Three
dimensional diagrams illustrate the Bengal Fan and the Monterey Canyon and Fan.
Ancient Mesozoic deep sea fan deposits of the California Coast Ranges are examined.
Primary inorganic structures of turbidites are illustrated. 2O slides and guide.

CONTENT SAMPLE: 25547 Monterey Canyon Fan. The Monterey submarine canyon
begins in the shallow water off Monterey, California, where the Salinas River flows into the ocean.
The canyon extends down the continental slope and branches out across its submarine fan which
is over 160 km (100 miles) from land.

The headward portion of the canyon acts as a giant sediment trap. North-to-south
moving longshore currents carry sediment into the canyon, where slumping and turbidity currents
transfer the material further down the canyon into deeper water. By the time the sediment
reaches the mouth of the canyon and the proximal portion of the fan, it has been reworked many
times by turbidity currents. Massive turbidity currents flowing down channels of their own making
carry sediment across the fan surface. Generally the coarsest sediment is deposited in the fan
channels and in the proximal portion of the fan. Finer sediment reaches the distal or outer part of
the fan which is farthest from the shoreline.

REVIEWS: "Recommended." Library Journal. "...clear and well organized..."
Booklist.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SEA-FLOOR SPREADING Slides order #SS-0760S ..........$34.95

Highlights the theories of modern geology: continental drift, sea-floor spreading,
and plate tectonics. Discusses evidence of early land-mass arrangement, and biological
phenomena, the idea of moving crust blocks is introduced, and origins of ocean and land
topography are explored. 10 frames, cassette and guide. (Filmstrip order SS-0760F
............$15.00.)

CONTENT SAMPLE: 3. The earth’s crust apparently consists of at least six large
blocks. These six principal crustal blocks are illustrated in this frame. They are generally larger
than individual continents and include both continental areas and parts of the ocean floor. Their
perimeters do not correspond to the classical continent-ocean boundaries. Instead their margins
are regions in which crust is either being formed (+) or destroyed (-). These margins are geolog-
ically active regions that are noted for their earthquakes, volcanoes, and ongoing mountain
building. The crustal blocks themselves are apparently rigid.

Each of these crustal blocks is moving relative to the others at slow but measurable
rates. Boundaries with “plus” marks in this illustration are regions where new crust is being
formed. Here the blocks are pushed apart on either side of mid-ocean ridges. The blocks converge
along the boundaries with “minus” marks. These are regions of deep ocean trenches or active
mountain building.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

seafl_t13 Earth's crustal blocks. graphic by Educational Images Ltd.

Copyright (c) MCMXCVII Educational Images Ltd., Elmira, NY, USA. All rights reserved.

EDUCATIONAL IMAGES LTD.

P.O.Box 3456 Westside Station

Elmira, N.Y., USA, 14905-0456

Telephone: 800-527-4264; 607-732-1090

Fax: 607-732-1183

E-Mail: edimages@edimages.com