Lab 9: The Effects of Sea Level Changes

SJSU Geol 4L Planet Earth Lab Lab 9 p. 1 of 7
Lab 9: The Effects of Sea Level Changes
In this lab, we will investigate the effects on Earth and its inhabitants of rising sea level.
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I. The World’s Oceans & Seas
Before we investigate the effects of sea level, we’ll review the locations of major bodies of water
around the globe. Label the following features on the map on the next page using the abbreviations
in parentheses. Clues are provided to help you determine the locations of most of them.
Atlantic Ocean (AtO)
Pacific Ocean (PO)
Indian Ocean (IO)
Arctic Ocean (ArO)
Persian Gulf (PG)
Red Sea (RS)
Gulf of Califorrnia (GC)
Bering Sea (BS)
Caribbean Sea (CbS)
Mediterranean Sea (MS)
Gulf of Mexico (GM)
Caspian Sea (CS)
Hudson Bay (HB)
You shouldn’t need a clue for this one.
Ditto for this one.
The smallest of the three main oceans.
Some geographers don’t consider it a real ocean; it’s covered with
ice for much of the year.
Oil-rich, bordered by Kuwait, Saudi Arabia, Iraq, and Iran.
Contains a young divergent plate boundary.
Separates Baja from the rest of Mexico; aka the Sea of Cortes.
Not far from the Bering Strait.
Bounded by Cuba, Venezuela, and Central America.
You should know this one.
Oil-rich, much to the delight of Texans and Mexicans
Not really a sea, but a huge landlocked lake near Azerbaijan.
O-h-h-h, Ca-a-nada-a-a-a.

SJSU Geol 4L Planet Earth Lab Lab 9 p. 2 of 7

SJSU Geol 4L Planet Earth Lab Lab 9 p. 3 of 7
II. Causes of Sea-Level Change
Many types of geologic studies indicate that
global sea level must have changed many times in
the past, at times higher and at times lower than
current sea level. For instance, the drowned river
channels that are cut into the floors of San Francisco
Bay and San Pablo Bay (diagram at right)
must have formed when sea level was lower and
the ocean coastline was west of the Golden Gate.
The entire bay system is a back-flooded stream
drainage.
A. Why would sea level change
Three possible reasons are climate, plate tectonics, and pumping.
1. Climate change: When air temperature decreases, less glacial ice melts, glaciers grow
in thickness and extent, and sea level falls (a “glacial” period). Conversely, warmer air
temperatures melt glaciers and raise sea level (an “interglacial”—our current situation).
2. Plate tectonics: The Earth’s surface may be pushed up or down by forces acting at plate
boundaries. For example, the northern edge of Australia is colliding with Indonesian islands,
shoving them upward and causing a drop in sea level from the islands’ perspective.
3. Pumping: Pumping of underground water or hydrocarbons (gas, oil) can cause the land
surface to sink. If this happens along a coastline, water will flood the sinking region,
causing a rise in sea level from the land’s perspective.
1. Which of the three reasons describe above, acting on its own, i.e., independently of the other
two reasons, could cause sea-level rise in the following combinations of coastal areas
1 2 3 Antarctica
1 2 3 Florida
1 2 3 San Francisco Bay area
1 2 3 Antarctica, San Francisco Bay area
1 2 3 Florida, San Francisco Bay Area
1 2 3 Antarctica, Florida, San Francisco Bay Area

SJSU Geol 4L Planet Earth Lab Lab 9 p. 4 of 7
III. Impacts of Sea Level Rise
A. Beringia and Immigration to North America
The two maps below show the modern ranges of reindeer and caribou. Unlike large mammals at
lower latitudes, which tend to have geographically limited ranges, reindeer and caribou are found
over a huge range—the entire width of two separate continents. Their puzzlingly broad range can
be explained by considering changes of sea level.
Asia and North America are separated by the narrow, shallow Bering Strait—but remember that
Earth currently is in an interglacial period. During glacial periods, sea level drops and Eurasia
and North America are connected as a single continent. Over many glacial-interglacial cycles,
many land animals have been able to migrate back and forth across the exposed low-lying land
connection, which is known as Beringia (buh-RIN-jee-ah).
Reindeer and caribou weren’t the only animals to cross Beringia. Most anthropologists think that
the ancestors of Native Americans migrated on foot from Asia to North America via Beringia.
Examine the maps on Plate 5, which show reconstructions of Beringia starting 13,000 years ago.
1. When would the migration route have become impassable due to rising sea level (circle one)
a. 12,000 to 11,000 years ago b. 11,000 to 10,000 years ago
c. 10,000-9,000 years ago d. 9,000-8,000 years ago
2. During which 1000-year period was the most land area flooded
a. 13,000 to 12,000 years ago b. 12,000 to 11,000 years ago
c. 10,000-9,000 years ago d. 9,000-8,000 years ago
3. Why wasn’t the land surface covered at a constant rate Briefly explain two possible reasons.

SJSU Geol 4L Planet Earth Lab Lab 9 p. 5 of 7
B. California During and Since the Last Ice Age
Consult the color maps (Plates 4 and 6) that show modern California and late Pleistocene California
(about 18,000 years ago, at the height of the last Ice Age). Light green areas on the late
Pleistocene map were exposed continental land surfaces.
1. Briefly contrast the late Pleistocene and modern geography and water resources of:
a. Coastal California
b. The Central Valley (Sacramento & San Joaquin)
c. The Sierra Nevada, and the region east of the southern Sierra Nevada

SJSU Geol 4L Planet Earth Lab Lab 9 p. 6 of 7
2. On this 1895 map, what geographic feature is shown south of Hanford in Kings County
(southeastern corner of the map) _________________________
3. Is this feature on the late Pleistocene map __________
4. Is it on the modern map ________
5. Suggest an explanation for the change in this feature’s appearance over time.

SJSU Geol 4L Planet Earth Lab Lab 9 p. 7 of 7
C. Sea-level Rise in the South Bay
Use the 11” x 17” excerpt of the topographic map of Mountain View, CA. The contour interval
of this map is 5’ (5 feet).
1. Using a colored pencil, shade in all areas that have elevations of 20’ or lower (this will include
the salt evaporation ponds in the bay).
The area you have shaded shows the effect of a 20-foot-rise in sea level if humans
were unable or unwilling to construct sufficient dikes to keep the water out.
2. Find each of the following six features on the map. Circle (in the list below, not on the map)
those that would be affected by rising sea level:
Runways at Moffett Field
Shoreline Theater (Shoreline at MV Park)
Sunnyvale Municipal Golf Course Intersection of San Antonio Rd. and U.S. 101
Sunnyvale Baylands Park
The aqueduct near U.S. 101 in Sunnyvale
3. Use a different color or pattern to show the area that lies between the 20’ and 40’ contours.
This shows the additional area that would be flooded if sea level rose another 20’.
4. Which increment of sea-level rise affected a larger area Circle one:
a. the first 20-foot rise (from 0’ to 20’) b. the second 20-foot rise (from 20’ to 40’)
5. In complete sentences, explain why the two 20-foot rises covered different areas.