Why Does Earth’s Surface Look the Way It Does?
Earth’s surface is shaped by dramatic features such as towering mountains, deep ocean trenches, chains of volcanoes, and vast mid-ocean ridges. Some regions experience frequent earthquakes, while others remain stable and quiet. Why do these patterns exist, and what processes lie beneath the surface to create them?
Why Does Earth’s Surface Look the Way It Does?
In this lesson, you will investigate real scientific evidence, including earthquakes, volcanoes, fossils, and Earth’s internal structure, to uncover the story of plate tectonics, the theory that explains the dynamic nature of our planet.
Start the Investigation →
Alfred Wegener: A Bold Hypothesis
In 1912, German scientist Alfred Wegener proposed the idea of continental drift. He suggested that Earth’s continents were once joined together in a single landmass called Pangaea and had slowly drifted apart. Most scientists at the time rejected his idea because Wegener could not explain how the continents moved. Still, his evidence from the fit of the continents, fossil discoveries, and ancient climate clues kept the idea alive. Next, you will explore the fossil evidence Wegener used to support his hypothesis.
What Do the Fossils Tell Us?
Explore the fossil evidence by clicking the circles. Pay attention to what kind of organism it was and where it lived.
What Do the Fossils Tell Us?
Mesosaurus was a small reptile that lived in freshwater. Fossils are found in both South America and Africa. What does this suggest?
Mesosaurus swam across the Atlantic Ocean.
South America and Africa were once connected.
Mesosaurus could live in saltwater too.
Fossils formed in the same place by coincidence.
What Do the Fossils Tell Us?
Glossopteris was a plant with heavy seeds that could not float far in water. Fossils are found on five continents. What does this suggest?
The seeds were carried across the oceans by waves.
Glossopteris evolved separately in each place.
Birds carried the seeds across the oceans.
These continents were once part of the same landmass.
What Do the Fossils Tell Us?
Lystrosaurus was a land reptile (a therapsid) that could not swim. Fossils are found in Africa, India, and Antarctica. What does this suggest?
Lystrosaurus could cross oceans by floating.
It lived on boats carried by ancient people.
These continents were connected in the past.
Antarctica used to be closer to the equator.
Where Do Earthquakes and Volcanoes Happen?
Begin your investigation by clicking the circle on the map. Study the earthquakes and volcanoes you see. Each time you explore, a new circle will appear until you have uncovered all three regions.
Next
What Do the Fossils Tell Us?
You explored earthquakes and volcanoes in three regions of the world. What do these patterns suggest?
Earthquakes and volcanoes happen randomly.
Earthquakes and volcanoes occur in clear patterns, often forming long belts.
Earthquakes and volcanoes are only found on land.
Where Do Earthquakes and Volcanoes Happen?
Begin your investigation by clicking the circle on the map. Study the earthquakes and volcanoes you see. Each time you explore, a new circle will appear until you have uncovered all three regions.
Next
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
Correct! Correct! Earthquakes and volcanoes form belts and lines that mark the edges of Earth’s plates.
Continue
❌ Incorrect: There’s no evidence of birds carrying heavy seeds across vast oceans millions of years ago. Try Again!
Now look at the middle of the Atlantic Ocean. How are the earthquakes arranged? Do you see any pattern along the ocean floor?
Mesosaurus
What it was: A small freshwater reptile, about 1 meter long. When it lived: Early Permian (~299–280 million years ago). Where it lived: Water (freshwater rivers and lakes).
❌ Incorrect: Mesosaurus lived only in freshwater rivers and lakes. It could not survive in salty ocean water, so it could not have crossed the Atlantic. Try Again!
✅ Correct: Identical Lystrosaurus fossils found on distant continents indicate that they were once part of a larger, previously joined group. Try Again!
Continue
Mesosaurus
What it was: A small freshwater reptile, about 1 meter long. When it lived: Early Permian (~299–280 million years ago). Where it lived: Water (freshwater rivers and lakes).
✅ Correct! Identical Mesosaurus fossils on both continents show they were once joined together.
Continue
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
Finally, explore the west coast of South America. What do you notice about the locations of earthquakes and volcanoes compared to the mountains?
Lystrosaurus
What it was: A pig-sized, plant-eating reptile (a therapsid — a mammal-like reptile). When it lived: Late Permian to Early Triassic (~260–250 million years ago). Where it lived: Land.
Cynognathus
What it was: A dog-sized carnivorous therapsid (mammal-like reptile). When it lived: Early to Middle Triassic (~250–240 million years ago). Where it lived: Land.
❌ Incorrect: Lystrosaurus lived about 250 million years ago — long before humans existed. Try Again!
❌ Incorrect: Fossil evidence and body structure show it was strictly freshwater. There’s no evidence that it lived in the oceans. Try Again!
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
✅ Correct: Glossopteris fossils across South America, Africa, India, Antarctica, and Australia show the continents were once connected.
Continue
❌ Not quite. The evidence shows they are not scattered everywhere. Try Again!
❌ Incorrect: The fossils are of the exact same species. If they had evolved separately, the plants would be different, not identical. Try Again!
Explore the edges of the Pacific Ocean. What do you notice about the earthquakes and volcanoes here? Are they scattered randomly, or do they form a shape around the ocean?
Cynognathus
What it was: A dog-sized carnivorous therapsid (mammal-like reptile). When it lived: Early to Middle Triassic (~250–240 million years ago). Where it lived: Land.
Lystrosaurus
What it was: A pig-sized, plant-eating reptile (a therapsid — a mammal-like reptile). When it lived: Late Permian to Early Triassic (~260–250 million years ago). Where it lived: Land.
❌ Incorrect: As a land animal, it had no adaptations for floating or swimming across oceans. Try Again!
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
❌ Incorrect: Glossopteris seeds were too heavy to travel long distances by water. Try Again!
⚠️ Partly true: Antarctica’s climate was warmer in the past, which allowed plants and animals to live there. But this alone doesn’t explain why the same fossils are also found in Africa and India. Try Again!
Now look at the middle of the Atlantic Ocean. How are the earthquakes arranged? Do you see any pattern along the ocean floor?
Not quite. Many are found in the ocean too, especially along the mid-ocean ridges. Try Again!
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
❌ Incorrect: The Mesosaurus fossils found in South America and Africa belong to the same species. If they had appeared by chance in two places, we’d expect different but similar reptiles — not identical fossils. Try Again!
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
Explore the edges of the Pacific Ocean. What do you notice about the earthquakes and volcanoes here? Are they scattered randomly, or do they form a shape around the ocean?
Finally, explore the west coast of South America. What do you notice about the locations of earthquakes and volcanoes compared to the mountains?
Lystrosaurus
What it was: A pig-sized, plant-eating reptile (a therapsid — a mammal-like reptile). When it lived: Late Permian to Early Triassic (~260–250 million years ago). Where it lived: Land.
Why Does Earth’s Surface Look the Way It Does?
Mary Clark
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Transcript
Why Does Earth’s Surface Look the Way It Does?
Earth’s surface is shaped by dramatic features such as towering mountains, deep ocean trenches, chains of volcanoes, and vast mid-ocean ridges. Some regions experience frequent earthquakes, while others remain stable and quiet. Why do these patterns exist, and what processes lie beneath the surface to create them?
Why Does Earth’s Surface Look the Way It Does?
In this lesson, you will investigate real scientific evidence, including earthquakes, volcanoes, fossils, and Earth’s internal structure, to uncover the story of plate tectonics, the theory that explains the dynamic nature of our planet.
Start the Investigation →
Alfred Wegener: A Bold Hypothesis
In 1912, German scientist Alfred Wegener proposed the idea of continental drift. He suggested that Earth’s continents were once joined together in a single landmass called Pangaea and had slowly drifted apart. Most scientists at the time rejected his idea because Wegener could not explain how the continents moved. Still, his evidence from the fit of the continents, fossil discoveries, and ancient climate clues kept the idea alive. Next, you will explore the fossil evidence Wegener used to support his hypothesis.
What Do the Fossils Tell Us?
Explore the fossil evidence by clicking the circles. Pay attention to what kind of organism it was and where it lived.
What Do the Fossils Tell Us?
Mesosaurus was a small reptile that lived in freshwater. Fossils are found in both South America and Africa. What does this suggest?
Mesosaurus swam across the Atlantic Ocean.
South America and Africa were once connected.
Mesosaurus could live in saltwater too.
Fossils formed in the same place by coincidence.
What Do the Fossils Tell Us?
Glossopteris was a plant with heavy seeds that could not float far in water. Fossils are found on five continents. What does this suggest?
The seeds were carried across the oceans by waves.
Glossopteris evolved separately in each place.
Birds carried the seeds across the oceans.
These continents were once part of the same landmass.
What Do the Fossils Tell Us?
Lystrosaurus was a land reptile (a therapsid) that could not swim. Fossils are found in Africa, India, and Antarctica. What does this suggest?
Lystrosaurus could cross oceans by floating.
It lived on boats carried by ancient people.
These continents were connected in the past.
Antarctica used to be closer to the equator.
Where Do Earthquakes and Volcanoes Happen?
Begin your investigation by clicking the circle on the map. Study the earthquakes and volcanoes you see. Each time you explore, a new circle will appear until you have uncovered all three regions.
Next
What Do the Fossils Tell Us?
You explored earthquakes and volcanoes in three regions of the world. What do these patterns suggest?
Earthquakes and volcanoes happen randomly.
Earthquakes and volcanoes occur in clear patterns, often forming long belts.
Earthquakes and volcanoes are only found on land.
Where Do Earthquakes and Volcanoes Happen?
Begin your investigation by clicking the circle on the map. Study the earthquakes and volcanoes you see. Each time you explore, a new circle will appear until you have uncovered all three regions.
Next
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
Correct! Correct! Earthquakes and volcanoes form belts and lines that mark the edges of Earth’s plates.
Continue
❌ Incorrect: There’s no evidence of birds carrying heavy seeds across vast oceans millions of years ago. Try Again!
Now look at the middle of the Atlantic Ocean. How are the earthquakes arranged? Do you see any pattern along the ocean floor?
Mesosaurus
What it was: A small freshwater reptile, about 1 meter long. When it lived: Early Permian (~299–280 million years ago). Where it lived: Water (freshwater rivers and lakes).
❌ Incorrect: Mesosaurus lived only in freshwater rivers and lakes. It could not survive in salty ocean water, so it could not have crossed the Atlantic. Try Again!
✅ Correct: Identical Lystrosaurus fossils found on distant continents indicate that they were once part of a larger, previously joined group. Try Again!
Continue
Mesosaurus
What it was: A small freshwater reptile, about 1 meter long. When it lived: Early Permian (~299–280 million years ago). Where it lived: Water (freshwater rivers and lakes).
✅ Correct! Identical Mesosaurus fossils on both continents show they were once joined together.
Continue
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
Finally, explore the west coast of South America. What do you notice about the locations of earthquakes and volcanoes compared to the mountains?
Lystrosaurus
What it was: A pig-sized, plant-eating reptile (a therapsid — a mammal-like reptile). When it lived: Late Permian to Early Triassic (~260–250 million years ago). Where it lived: Land.
Cynognathus
What it was: A dog-sized carnivorous therapsid (mammal-like reptile). When it lived: Early to Middle Triassic (~250–240 million years ago). Where it lived: Land.
❌ Incorrect: Lystrosaurus lived about 250 million years ago — long before humans existed. Try Again!
❌ Incorrect: Fossil evidence and body structure show it was strictly freshwater. There’s no evidence that it lived in the oceans. Try Again!
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
✅ Correct: Glossopteris fossils across South America, Africa, India, Antarctica, and Australia show the continents were once connected.
Continue
❌ Not quite. The evidence shows they are not scattered everywhere. Try Again!
❌ Incorrect: The fossils are of the exact same species. If they had evolved separately, the plants would be different, not identical. Try Again!
Explore the edges of the Pacific Ocean. What do you notice about the earthquakes and volcanoes here? Are they scattered randomly, or do they form a shape around the ocean?
Cynognathus
What it was: A dog-sized carnivorous therapsid (mammal-like reptile). When it lived: Early to Middle Triassic (~250–240 million years ago). Where it lived: Land.
Lystrosaurus
What it was: A pig-sized, plant-eating reptile (a therapsid — a mammal-like reptile). When it lived: Late Permian to Early Triassic (~260–250 million years ago). Where it lived: Land.
❌ Incorrect: As a land animal, it had no adaptations for floating or swimming across oceans. Try Again!
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
❌ Incorrect: Glossopteris seeds were too heavy to travel long distances by water. Try Again!
⚠️ Partly true: Antarctica’s climate was warmer in the past, which allowed plants and animals to live there. But this alone doesn’t explain why the same fossils are also found in Africa and India. Try Again!
Now look at the middle of the Atlantic Ocean. How are the earthquakes arranged? Do you see any pattern along the ocean floor?
Not quite. Many are found in the ocean too, especially along the mid-ocean ridges. Try Again!
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
❌ Incorrect: The Mesosaurus fossils found in South America and Africa belong to the same species. If they had appeared by chance in two places, we’d expect different but similar reptiles — not identical fossils. Try Again!
Glossopteris
What it was: A seed fern with tongue-shaped leaves. When it lived: Late Paleozoic (~299–252 million years ago). Where it lived: Land (grew in swamps and floodplains).
Explore the edges of the Pacific Ocean. What do you notice about the earthquakes and volcanoes here? Are they scattered randomly, or do they form a shape around the ocean?
Finally, explore the west coast of South America. What do you notice about the locations of earthquakes and volcanoes compared to the mountains?
Lystrosaurus
What it was: A pig-sized, plant-eating reptile (a therapsid — a mammal-like reptile). When it lived: Late Permian to Early Triassic (~260–250 million years ago). Where it lived: Land.