Chapter 5, Google Earth Project - W.H. Freeman

Google Earth Project
Southern limit of
Great Barrier Reef
Data SIO, NOAA, U.S. Navy, NGA, GEBCO
©2009 Cnes/Spot Image
Image ©2009 TerraMetrics
Image ©2009 DigitalGlobe
Sediments are deposited in specific geologic environments where the formation of sedimentary rock
takes place. Specifically, the processes that transform sediment into sedimentary rock happen near Earth’s
surface and always involve the presence of liquid water in some form. Thus, Google Earth is an ideal tool
for interpreting and appreciating the spectrum of environments in which sedimentary rocks form.
Among these unique sedimentary environments are carbonate platforms. These platforms form
when ions dissolved in seawater precipitate to form carbonate sediments. This process is often controlled
by organisms. Consider the Great Barrier Reef off the northeastern coast of Australia. Here you
will see a sedimentary environment driven by the life cycles of small marine organisms and the calciteenriched
water that they live in. What causes the distinctive blue-green color of the water here, and how
are soluble minerals such as CaCO 3
precipitated as sediment on the ocean floor Appreciate the geometry
of the reef feature and its geographic limits to the north and south. Now compare the geometry of
the Great Barrier Reef with a slightly different carbonate environment. Travel down to the equatorial
waters of Bora Bora atoll in the South Pacific Ocean and see how the carbonate deposits there differ.
Why does the reef take its circular shape, and what inspired it to begin growing here These questions
and many more can be explored though the GE interface.
Location Great Barrier Reef, northeastern Australian coast, and Bora Bora Atoll, South Pacific Ocean
Goal Explore an area of significant sediment deposition in a modern sedimentary environment
Linked Figure 5.18 and Earth Issues 5.1
1. Navigate to the Great Barrier Reef on the northeastern
coast of Australia and zoom in to an eye altitude of
20 km on Pipon Island, Queensland, Australia. Notice
the white material around the island itself and along
the coast of the peninsula just to the south (on mainland
Australia). Based on your investigation of the images here
(feel free to zoom in and out), how would you best characterize
this white material Be sure to consider any pat-
© 2010 W.H. Freeman and Company

terns you see in the distribution of this coastal material
when choosing an answer.
a. Unconsolidated carbonate sediment
b. Large boulder deposits
c. Cemented olivine sand
d. Deltaic siliciclastic mudstone
2. From Pipon Island, zoom out to an eye altitude of
2300 km and appreciate the length of the offshore
reef features paralleling the coast. Use the path
measurement tool in GE to determine the approximate
length of this reef system.
a. 2000 km
b. 1400 km
c. 2800 km
d. 750 km
3. Notice that the Great Barrier Reef provides some protection
to the coastal environment where it is present.
As you follow the reef to the south, it becomes
less distinct and provides less coastal protection. At
the southern end of the reef, waves from the open
South Pacific are free to break on the Australian coast,
and some of the best surfing in the world results. At
approximately what southerly latitude does the reef
system end
a. 10°30'23'' S; 143°30'06'' E
b. 17°56'25'' S; 146°42'57'' E
c. 24°39'49'' S; 153°15'18'' E
d. 21°06'31'' S; 151°38'53'' E
4. Following up on questions 2 and 3, the Great Barrier
Reef provides protection to the Australian coastline
and allows for sedimentary processes to occur there.
As one moves farther from the equator to latitudes
of 25° S, it is clear that reef formation stops. Consider
the conditions in which reef-building organisms
precipitate calcium carbonate. What might be
the primary climate-related factor controlling the
southern limit of the Great Barrier Reef
a. Sea surface temperatures of less than 18°C
b. The depth of ocean water along the coast to the
south
c. The amount of sediment on the beaches near
Brisbane
d. The color of the seawater along the coast south
of 25°
Optional Challenge Question
5. Now let’s travel to warmer climes by typing “Bora
Bora atoll” into the GE search window and zooming
in to an eye altitude of 20 km once you arrive there.
In contrast to the Great Barrier Reef, this island in
the South Pacific has a very limited reef system, yet
that reef system has a unique geometry. The formation
of an atoll like this one involves a unique relationship
between biotic and geologic factors. From
your observation and exploration of the atoll, which
pair of biotic and abiotic factors properly reflects the
relationship present here
a. Birds and quartz sand beaches
b. Coral reefs and volcanic islands
c. Foraminifera and outcrops of marine shale
d. Whales and carbonate platforms
© 2010 W.H. Freeman and Company