The Earth Flashcards
When the Earth first formed, what was it?
Completely molten (hot liquid)
How old do scientists estimate the Earth may be?
About 4500 million years old
How did they estimate this?
Because the Earth has to be older than the oldest rocks
Hold old are the oldest rocks?
Almost 4000 million years old
What does studying rocks tell us?
The Earth’s structure and how it has changed
What processes change the Earth?
- Erosion
- Craters
- Mountain formation
- Folding
What is Erosion?
The Earth’s surface is made of rock layers, one on top of another. The oldest usually at the bottom. The layers are compacted sediment, produced by weathering and erosion. Erosion changes the surface over time.
What are Craters?
The Moon’s surface is covered with impact craters from meteors. Meteors also hit the Earth but craters have been erased by erosion.
What is Mountain Formation?
If new mountains weren’t being formed, the Earth’s surface would have been eroded down to sea level
What is Folding?
Some rocks look as if they’ve been folded in half. This required huge force over a long time.
What other evidence of the Earth’s age can be found?
By studying;
- Fossils of plants and animals in sedimentary rock layers, which show life has been changed
- The radioactivity of rocks. A rock’s radioactivity decreases over time and radioactive dating measures radiation levels to find out a rock’s age.
