Fossil Evidence
These are remains or traces of organisms found in rock.
What are fossils?
Matching rock layers on different continents suggest continents were once ______.
What is connected?
Continents like South America and Africa look like they fit together like a ______.
What is a puzzle?
The youngest ocean crust is found near these underwater features.
What are mid-ocean ridges?
The movement of Earth’s plates is called ______.
What is plate tectonics?
A possible explanation that can be tested is called a ______.
What is a hypothesis?
Why do identical fossils on different continents suggest plate movement?
Because organisms could not cross oceans, so continents must have been connected.
Why are matching mountain ranges on different continents important evidence?
They formed together and were later separated by plate movement.
Why do scientists look at continental shelves instead of coastlines?
Shelves match more accurately because coastlines change due to erosion.
What pattern is found on both sides of mid-ocean ridges?
Symmetrical magnetic striping.
What causes plates to move slowly over time?
Mantle convection (heat-driven movement inside Earth).
Why is “it’s a coincidence” a weak scientific explanation?
It does not explain patterns or provide evidence-based reasoning.
Fossils of a freshwater reptile are found on two continents separated by an ocean. What does this suggest?
The continents were once connected.
You discover rocks with the same age and composition on two continents. What should you conclude?
They were once part of the same landmass.
A student says continents fit together, so that proves movement. What should you add to strengthen this idea?
Use continental shelf data and other evidence like fossils or rocks.
New crust forms at ridges and pushes older crust away. What process is this?
Seafloor spreading.
If new crust is forming, what must be happening to older crust?
It is moving away (and may be subducted).
A scientist uses fossils, rocks, and seafloor data together. Why is this stronger than just one type of evidence?
Multiple lines of evidence support the same conclusion.
How is fossil evidence similar to rock evidence in supporting plate motion?
Both show patterns across continents that suggest they were once connected.
Why is rock evidence stronger than continental shape alone?
It includes measurable data (age, composition), not just visual similarity.
Why is continental shape considered weaker evidence than seafloor data?
It is observational and can be affected by erosion.
Why is symmetrical magnetic striping strong evidence for plate movement?
It shows a repeated, predictable pattern of crust forming and moving outward.
How does seafloor spreading provide evidence AND explain movement?
It shows both the process (new crust forming) and the movement of plates.
How do fossils, rocks, and seafloor evidence work together in a model of plate tectonics?
They each show different parts of the same system—fossils and rocks show continents were once connected, while seafloor evidence explains how plates move and spread apart.
A scientist argues fossils alone prove plate movement. Do you agree? Why or why not?
No—fossils show connection, but not how plates move.
Defend why matching rock layers are unlikely to be coincidence.
Matching age, composition, and structure across continents is too specific to happen randomly.
Evaluate this claim: “Continents fit together, so that proves plate tectonics.”
Partially true—needs additional evidence like fossils or seafloor data.
Why is seafloor spreading considered the strongest evidence of plate motion?
It shows the actual mechanism and movement of plates.
Construct a short explanation of how new crust forms and moves plates.
Magma rises, cools into rock, and pushes older crust outward.
Why did scientists reject continental drift at first, and what new evidence changed their thinking?
Scientists first rejected continental drift because there was no explanation for how continents could move. New evidence like seafloor spreading, magnetic striping, and mantle convection provided a mechanism, which helped scientists accept the theory.