Researching the Geology of Africa and South America
Your Role: Geologist
Geologists comb the landscape describing rock types
and large scale structures of the crust.
 They notice the boundaries between rock types.
The call these ‘contacts’ and draw them on maps
as lines.
 They notice and record the thickness and
orientation of rock layers. Are they horizontal or
tipped over at an angle.
 They notice if rock layers are bent into folds or ridges. When they are, they
measure the direction of an imaginary line along the ridge. Does it point northsouth, east-west or something in-between?
Background Information
Just as the pattern and color of jigsaw pieces match, the patterns and kinds of rocks
along the coasts of Africa and South America should match if the continents were once
connected. Geologists have mapped much of South America and Africa to learn about
the kinds, ages and folding of the rocks.
We cannot expect all the rocks to match because some
rocks may have formed after South America and Africa
separated. As the split occurred about 200 million years
ago, only rocks older than 200 million years should match.
The problem is difficult because many of these old rocks
lack fossils for determining their ages.
Besides comparing the ages of the rocks, the folding of the
rocks can be compared. If they are folded to form ridges or
mountain ranges, the directions of these ridges or mountains should match.
Data about the older rocks at some places are incomplete. Reasons for this are:
1) the older rocks may have been eroded away
2) the older rocks may have been covered by younger rocks or sediments
3) older rocks have been metamorphosed so they cannot be dated chemically
4) no older rocks were deposited, and
5) little information is available because the geologic studies of some areas are too
limited.
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Your Task:
1. You be given an assignment of mapping Africa or South America. You will
receive a map of your continent with numbers that represent field locations. You
will also receive some field notes that describe each location.
2. Read through the field notes below and present as them as directed on the maps
of Africa and South America. To do this, you will have to decide on a key for
ages. You could use a color or pattern. (Note: the lines of latitude and longitude are
not the boundaries for the colors).
3. Show the trends of the folds, or mountains, with a solid black line.
4. After your map is created meet with another geologist who has mapped the same
continent (Africa or South America) as you. Compare your maps. If there are
major differences, try to determine why. In the end they should be fairly similar.
5. Now meet another geologist who has mapped the OTHER continent (Africa or
South America) as you.
6. Discuss the evidence for continental drift. When fitted together, how well do the
ages of rocks match? Do the features, such as contacts and folds align?
7. Does the evidence of the rocks tend to support the idea that the continents may
have fitted together? What evidence refutes that conclusion? What are some
reasons you can think of for the match not being better?
8. Work together to create a brief presentation on your research. Your presentation
should include:
 A script of key points you will make to the whole group of scientists. You
should plan to share the conclusion of your analysis and support it with
evidence.
 A high quality graphic that shows the details of your discovery. You may
want to cut and paste your maps onto a small poster. It should have a
clear title and a descriptive caption.
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Field Notes
Table 1. Data for South America for Rocks at Points 1 to 16
1. There is a ‘contact’ between two rock types. Draw an east-west line through this
point to the coast. Make this line about 1 cm long. North of this line the rocks are
older than 2600 million years. South of this line the rocks are about 2000 million
years.
2. Rocks are about 2000 million years.
3. Draw a north-south line, about 1 cm long, through this point to the coast. West of
this boundary, rocks are 2000 millions years old. To the ease of this line, the rocks
are about 600 million years old.
4. 5. and 6. Connect these points with a smooth curved line ending at both ends at the
coast to form a small dish-shaped area. To the north of this line (within the dishshaped area) the rocks are 2000 million years old. To the south, the rocks are 600
million years.
7. Rocks here are 600 million years old and they are folded in a northeast-southwest
(NE-SW) direction. (Draw a dark line about 1 cm long to show this fold direction.)
8. Rocks are about 600 million years old and they are folded in an east-west direction.
(Draw a dark line about 1 cm long to show the fold direction.)
9. Draw an east-west line to show the boundary between 600 million old rocks to the
north and 2600 million old rocks to the south near the coast. (Data for this area
have been simplified.)
10. Rocks are about 2000 million years old and are folded north-south.
11. 12. 13. and 14. Rocks are mostly 600 million years old and have folds which trend
parallel to the coastline. This area is complicated and has some rocks, which are
1000 million years old.
15. Rocks are about 2000 million years old.
16. Rocks are about 2000 million years old and are folded in a northwest-southeast
(NW-SE) direction. (Show this with a line 1 cm perpendicular to the coast.
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Field Notes
Table 2. Data for Africa for Rocks at Points 21 to 39
21 & 22. Rocks are about 600 million years old. Draw a solid line between these points
to show the direction of folding of these rocks.
23. Draw a boundary line through this point, which trends NNW-SSE. (This is at an
angle of about 60 degrees with the longitude line.) Rocks to the west of the line are
600 million years (as at points 21 and 22) but rocks to the ease are older than 2600
million years.
24. Draw a boundary line northeast (NE) from the coast through this point to the
intersection of the latitude and longitude lines. Rocks to the northwest are older than
2600 million and rocks to the southeast (SE) are about 2000 million years.
25 & 26. Rocks are about 2000 million years old.
27 & 28. The boundary line connects these two points and extends to the coast. To the
west the rocks are about 2000 million years and to the east are about 600 million
years old. On the ease side of the line, draw one or two dark lines parallel to the
boundary line to show the direction of folds.
29. Rocks are about 600 million years. Data are lacking.
30 & 31. Draw a boundary line connecting these points and extending to the coast. The
rocks on the northwest (NW) are about 600 million years and the rocks to the southeast
(SE) are older than 2600 million years. On the north side, draw one of two dark lines
parallel to the boundary to show the direction of folds.
32. The rocks are about 600 million years old; use latitude line as boundary with older
rocks to the north. Draw a line parallel to the coast to show the direction of the folds.
33. Rocks are about 600 million years old. Draw a line parallel to the coast to show the
direction of the folds.
34. The rocks here are different; most are 1000 million years old and some are 1300 to
1700 years old. Draw a line to show that they are folded east-northeast to westsouthwest (ENE-WSW).
35. Rocks are about 600 million years old. Draw a northwest-southeast (NW-SE) line to
show the direction of the folds.
36. Rocks are about 1000 million years old. Draw an east-west line to show the
direction of folds.
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37. Rocks are about 600 million years old. Draw a northeast-southwest (NE-SW) line to
show the direction of folds.
38. Rocks are about 1000 million years old. Draw a northeast-southwest (NE-SW) line
to show the direction of folding.
39. Rocks are about 225 million years old, except for a few, which are 2000 million years
old at the southern tip of Africa. Draw a dark-east-west line to show the direction of
folding.
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