CH. 1.2 - Earth's Craters vs. Moon's Crater Preservation
Oct 2, 2024
Lecture Notes: Why Earth Has Fewer Impact Craters Than the Moon
Introduction
Earth exhibits fewer impact craters compared to the Moon.
The Earth is dynamic with geological activities that erase evidence of impact craters over time.
Examples of Meteorite Impact Craters on Earth
Meteorite Crater, Arizona
Size: Created by an object the size of an 18-wheel tractor trailer.
Characteristics: Ridge around the edge is from debris thrown out during impact.
Age: Less than 50,000 years old.
Namibia Crater, Southwest Africa
Size: Double the size of the Arizona crater.
Characteristics: Much shallower due to 4 million years of erosion.
Chicxulub Crater, Mexico
Significance: Impact that led to dinosaur extinction 65 million years ago.
Size: Gigantic, 156 miles in diameter.
Description: Crater is a mile underground, discovered through seismic imaging.
Impact Consequences: Fireball incinerated half the planet, debris blocked sunlight leading to mass extinction.
Resulted in a global layer rich in iridium and other impact evidence.
Discovery: Found by oil companies surveying for oil, found shattered rocks and glass.
Manicouagan Crater, Quebec, Canada
Observation: Seen from space, distinctive ring-shaped lake.
Characteristics: Size is about 60 miles across, over 200 million years old.
Formation: Impact at a higher altitude, later shaped by glacial erosion.
Glacial Action: Softer rock eroded by glaciers, forming a lake.
Geological Processes on Earth
Erosion and Deposition: Over time, craters are filled in, buried, and eroded away.
Plate Tectonics: Earth's surface is recycled; old plates subduct, and their features are lost.
Contrast with the Moon
The Moon lacks geological processes; its surface remains unchanged for billions of years.
Craters on the Moon are preserved due to lack of dynamic geological activity.
Conclusion
Earth's dynamic processes (erosion, deposition, tectonics) contribute to the removal of impact craters over time, unlike the Moon which remains geologically inactive.