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Using Data from Fossil Corals (Uplift Corals) to Understand
Tectonic Processes
Student worksheet
Name: _________________________________
Date: _____________________
Background
Barrier reef islands surrounding the coastlines of the New Georgia Islands represent a stage
in the sequence of atoll formation proposed by Charles Darwin in 1842. Barrier reefs and
atolls form as coral reefs anchored to volcanic islands grow upward to keep pace with actual
rising sea level, or apparent sea level rise due to subsidence of the islands. Emergent barrier
reefs also exist on the New Georgia Islands reaching up to 25 meters above sea level. Their
presence indicates the interruption of Darwin’s predicted subsidence sequence in the
formation of atolls by tectonic uplift, which has raised these coral reefs above sea level to
create islands capped by a series of coral reef terraces. Indeed, earthquakes provide
evidence that a recently active spreading center, the Gizo Ridge, is now subducting beneath
the New Georgia Islands generating tectonic uplift.
Materials

Map showing the location of the New Georgia Islands and sampling locations.

Data set (sampling locations, elevation above sea level, C-14 age data for coral reefs
sampled at about 30 locations in the New Georgia Islands)

Computer - PC or Mac (provided)

Vellum/tracing paper/transparency sheet for each student. Note that if
transparencies are used, then students will need special transparency markers.
Procedure
 Use
Alan
Jones’
Seismic
Eruption
software
program
(http://www.geol.binghamton.edu/faculty/jones) installed on the computers in the
classroom to see the locations of volcanoes and earthquakes in the SW Pacific and
explore the geologic setting of the Solomon Islands.

Using the data on the data sheet, calculate rates of tectonic uplift in mm/year for
the locations sampled. To do this you will use the elevation above current sea level
of the raised coral terraces and radiocarbon dates corresponding to the time at
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The TXESS Revolution Project. Funded by NSF
which the reefs were lifted out of the ocean—an event that killed them since corals
are marine organisms that can only survive in the ocean.

Plot the uplift rates that you have calculated for each sampling location on a sheet of
vellum, tracing paper or a transparency placed over the map in your packet. You
may draw contour lines using an appropriate interval, or color code uplift rates using
an appropriate range (0 – 0.9 mm/yr, 1.0 – 1.9 mm/yr, etc.). Determine whether the
data you’ve plotted on the map reveal different rates of tectonic uplift for the New
Georgia Islands.
Note: Instead of the two methods above, you may develop other creative ways of
depicting the data appropriate to the task. However, if you choose to create contour
maps, be sure to follow the basic rules of contouring.

Develop a conceptual model to explain the pattern of uplift for the last 10,000 years
that emerges from the data and share your results with the class.

Discuss the model presentations. The questions below are intended to guide the
discussion.
1. Where is uplift most pronounced?
2. Where is uplift the least pronounced?
3. What is causing the uplift? Make drawings to depict what you think is
happening and label the plates and the features.
4. Notice that there is a difference in the amount of displacement (uplift) as you
cross the New Georgia Islands from east to west. Why?
5. The data in this activity cover the past 10,000 years (Holocene epoch). Can
we assume that sea level remained constant during this time span?
6. There are fossil reefs that date back to older than 100,000 years in the New
Georgia Islands. Could we use C-14 to date these reefs?
Summative Assessment
Taylor, Mann and colleagues calculated rates of tectonic uplift by combining elevation data
with Carbon-14 dating of emergent reef terraces. By dating distinct notches in the reef
terraces, the researchers were also able to document the times of individual earthquake
events and amount of uplift associated with each earthquake. Their results are published in
the following articles:
Mann, P., F. W. Taylor, M. B. Lagoe, and A. Quarles (1998), Accelerating late Quaternary
uplift of the New Georgia Island Group (Solomon island arc) in response to
subduction of the recently active Woodlark spreading center and Coleman
Seamount, Tectonophysics, 295, 259 – 306.
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The TXESS Revolution Project. Funded by NSF
F. W. Taylor, F.W., Paul Mann, M. G. Bevis, R. L. Edwards, Hai Cheng, Kirsten B. Cutler, S.
C. Gray, G. S. Burr, J. W. Beck, David A. Phillips, G. Cabioch, and J. Recy (2005), Rapid
forearc uplift and subsidence caused by impinging bathymetric features: Examples
from the New Hebrides and Solomon arcs, Tectonics, Vol. 24, TC6005,doi:10.1029/
2004TC001650.
A. Read these papers and write a report comparing the scientists’ models and conclusions
with the different models and conclusions presented by the class groups.
B. Today, geophysicists continue to monitor plate motion in many different parts of the
world using the U.S. Global Positioning System (GPS). Currently, there are 24 GPS
satellites, each traveling in a 12-hour, circular orbit 20,200 kilometers above Earth. The
satellites are positioned so that six are observable nearly 100% of the time from any
point on Earth. The GPS satellites transmit ranging codes on two-radio frequency
carriers at L-band frequencies, which can be detected by ground-based GPS receivers
that researchers set up in the field. Special ground-based stations perform satellite
monitoring that permits the locations of GPS receivers to be determined with a high
degree of accuracy. Researchers are able to study the motions of tectonic plates,
displacements associated with earthquakes, sea level fluctuations, and Earth
orientations by monitoring very precisely the change in the receiver locations over time.
With the technology currently available, an accuracy of a few millimeters can be
achieved.
Write a report on the EarthScope Plate Boundary Observatory and its role in the larger
EarthScope experiment.
Web Links: http://pboweb.unavco.org/?pageid=53 ; http://www.earthscope.org/
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The TXESS Revolution Project. Funded by NSF
DATA SHEET
Island and Sampled Localitya
Rendova and Tetapare Islands
6. Asovo Point Peninsula
6. Asovo Point Peninsula
6. Asovo Point Peninsula
10. South Rava Point
7. Rano Village
8. South Mbarora Bay
8. South Mbarora Bay
8. South Mbarora Bay
8. South Mbarora Bay
12. W of Kioroso River
Ranongga Island
14. Kukuri Point
15.N of Konggu Village
16. Pienuna Village
18. S of Kolomali Village
18. S of Kolomali Village
New Georgia, Vangunu and Parara
Islands
26. Rereghana Island
47. Hotoanivena Island
57. Viru Harbor
57. Viru Harbor
39. West Maitu Island
33. Ramata Island
25. Roviana Island
27. Ararosa Pass
29. Vululi Point North
29. Vululi Point North
Kolombangara Island
63. Ruvi Bay
61. Unnamed islet S of Vila Point
Ghizo Island
67. Logha Island
Simbo Island
70. Nusasimbo Island
Vella Lavella Island
72. Maravari Village
77. Paramata
73. Northeast Lambulambu
Height
(above SL
in mm)
Ageb
(yr B.P.)
6.5
18.0
18.1
1.6
28.0
11.9
1.7
15.7
22.1
46.8
6500
18000
18100
1600
28000
11900
1700
15700
22100
46750
2630.00
4910.00
6690.00
5170.00
5430.00
5340.00
600.00
4845.00
5520.00
7430.00
11.9
32.0
14.0
1.4
1.6
11900
32000
14000
1430
1630
3620.00
7025.00
4355.00
470.00
590.00
157°17′
157°32′
157°17′
157°17′
0.4
0.8
6.5
4.1
2.0
2.6
3.0
3.6
1.6
4.9
420
750
6500
4100
2000
2610
3000
3600
1630
4900
180.00
6430.00
5500.00
5570.00
4120.00
6100.00
6220.00
6430.00
720.00
6810.00
8°04′
8°07′
156°57′
157°3′
1.0
3.3
1000
3260
2250.00
4330.00
8°02′
156°47′
1.0
1000
5340.00
8°07′
156°32′
1.0
1000
5490.00
7°50′
7°44′
7°41′
156°41′
156°32′
156°47′
1.0
1.0
1.0
1000
1000
1000
6180.00
870.00
6490.00
Lat.
(S)
Long.
(E)
8°35′
8°35′
8°35′
8°41′
8°38′
8°40′
8°40′
8°40′
8°40′
8°43′
157°20′
157°20′
157°20′
157°19′
157°17′
157°18′
157°18′
157°18′
157°18′
157°37′
8°01′
156°36′
8°01′
8°01′
156°35′
156°35′
8°18′
8°44′
8°29′
8°29′
8°34′
157°23′
158°04′
157°35′
157°35′
158°08′
8°22′
8°22′
8°03′
8°03′
Height
(above living
coral, in m)
Uplift
Rate
(mm/yr)
a
All locality names from 1:100,000-scale published geol of Energy, Water, and Mineral Reservoir, Honiara,
Solomon Islands.
b
Standard radiocarbon age calculated with the 5568 yr or for the reservoir effect: all errors are 2.
(From, Mann, P., F. W. Taylor, M. B. Lagoe, A. Quarles, and G. Burr, 1998. Accelerating late Quaternary uplift of
the New Georgia Island Group (Solomon island arc) in response to subduction of the recently active Woodlark
spreading center and Coleman seamount: Tectonophysics, 295, 259-306.)
Site TXESS Revolution. Last Revised May 2011
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