Earth's Changing Surface — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. In undisturbed rock layers, the older layers are usually on the bottom.
The Law of Superposition says that in a stack of sedimentary rock, the oldest layers are at the bottom and the newest are on top.
2. The preserved remains or traces of ancient living things found in rocks are called fossils.
Fossils give scientists clues about past environments and how Earth's surface has changed over time.
3. A deep, narrow valley cut by a river over a long time is called a canyon.
Canyons are landforms made by long-term erosion, where rivers slowly carve down through rock.
4. Finding fossils of sea creatures on a mountain is evidence the area was once under the ocean.
Ocean fossils on mountains show that the rock formed underwater long ago and was later pushed up by Earth's plates.
5. A natural feature on Earth's surface, like a hill, valley, or mountain, is called a landform.
Landforms are clues to the slow and fast processes that shaped a region over time.
6. Mountains that form when two of Earth's plates push together and squeeze rock upward are called fold mountains.
Fold mountains, like parts of the Appalachians, are evidence that plates have pushed together over millions of years.
7. When sediment piles up at the mouth of a river, the flat fan-shaped landform is called a delta.
Deltas show deposition over many years where rivers slow down before entering a lake or ocean.
8. A scientist who studies rocks, layers, and Earth's history is called a geologist.
Geologists read rock layers and fossils like a history book to understand how Earth's surface has changed.
9. Layers of rock that form when sediment is pressed and stuck together are called sedimentary rock.
Sedimentary rock layers and the fossils inside them are key evidence of Earth's changing surface.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Canyon
→ Deep, narrow valley carved by a river over a long time
Triangle-shaped landform of dropped sediment at a river's mouth
Volcano
→ Mountain that forms when lava and ash pile up and harden
Preserved trace of an ancient plant or animal in rock
Fossil
→ Preserved trace of an ancient plant or animal in rock
Mountain that forms when lava and ash pile up and harden
Delta
→ Triangle-shaped landform of dropped sediment at a river's mouth
Deep, narrow valley carved by a river over a long time
Connecting names to descriptions helps Grade 4 students recognize the slow and fast processes that build Earth's features.