Continental Drift Detectives

What does the match in rock layer age and folding structure indicate?

How do diamond-bearing rock formations in Africa & Brazil support this?

Evidence Line 4: Paleoclimate (Glacial Scars & Tropical Coal)

Paleoclimatology

1. Glacial Striations in the Tropics

Deep gouges in bedrock caused by massive ice sheets found in warm southern Africa, India, and Australia.

Explain why this requires continents to have been near the South Pole:

2. Tropical Coal Beds in Antarctica

Thick seams of sedimentary coal (formed from dense tropical swamp vegetation) discovered beneath Antarctic ice.

What does this prove about Antarctica's past location and climate?

3

The Skeptics' Challenge: The Missing Mechanism

Despite Wegener's extensive evidence, the scientific community in the 1920s largely rejected his hypothesis.

What vital question could Alfred Wegener NOT answer about HOW continents moved?

4

Case Conclusion: Claim • Evidence • Reasoning (CER)

SEPS.7: Scientific Argumentation

Prompt: Construct a short scientific argument answering: Which two lines of evidence provide the strongest proof that South America and Africa were once physically connected? Explain your reasoning.

Claim & Evidence:

Scientific Reasoning (Why this rules out other explanations):

Drift Detectives Guided Notes • Indiana Science Standards Page 2 of 2 • Assessment Ready

Appalachian & Caledonian match: The mountain rocks share the exact same age, rock sequences (sandstones, shales, limestones), and folded structural patterns. When the Atlantic is closed, they form a single continuous mountain chain created during Pangaea's collision.

Diamond/Kimberlite match: Unique volcanic diamond pipes in West Africa align directly with matching pipes in eastern Brazil, proving the cratons (continental cores) were welded together.

Evidence Line 4: Paleoclimate (Glacial Striations & Coal)

Glacial Striations: Massive continental ice sheets only form at polar latitudes or extreme high altitudes. Striations in equatorial regions radiate outward from a central cap that only makes sense if those continents were clustered near the South Pole.

Antarctic Coal: Coal forms from decaying lush tropical swamp plants. Antarctica could only have supported lush swamps if it were once located near the warm equator, not at the freezing South Pole.

Part 3: The Skeptics' Challenge (Why Wegener Was Rejected)

Wegener could not explain the mechanism—the physical force driving continental motion. He suggested continents plowed through oceanic crust like icebreakers due to tidal forces, which physicists proved impossible. Decades later in the 1960s, seafloor spreading and mantle convection proved tectonic plates move together.

Part 4 CER Exemplar (SEPS.7) Score: 4/4 Points

Exemplar Response: "South America and Africa were once physically connected as shown by the identical geometric continental shelf fit and matching fossils of the freshwater reptile Mesosaurus (Claim & Evidence). Because Mesosaurus lived only in freshwater lakes and could not survive swimming across thousands of miles of saltwater ocean, and the jagged continental shelf edges match within fractions of a percent, the only plausible scientific explanation is that the two landmasses were joined when the reptile lived and later rifted apart (Reasoning)."

Common Student Misconceptions & Corrections

Misconception 1: "Continents float on top of ocean water like boats." Scientific Reality: Continents are thick granite crust that sit atop rigid tectonic plates floating on the semi-fluid asthenosphere (mantle).

Misconception 2: "The climate of the whole Earth just got cold then hot." Scientific Reality: Tropical coal and glaciers existed at the exact same geological time period (~300 Ma), proving regional latitude shifts, not whole-Earth swings.

Drift Detectives Teacher Guide • Indiana Academic Standards Page 2 of 2 • Classroom Ready