290 likes | 385 Vues
Explore the dynamics of impacts on Earth, from small pit craters to large multiple-ring basins. Learn about the impact process, recognizing craters on Earth, and the formation of the moon. Discover the mysteries of comets, asteroids, and planetary history through a scientific lens.
E N D
Impact! Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
The Solar System • Nine Eight Planets • Over 100,000 catalogued asteroids • ???? Centaurs • ???? KBO’s (including one disgruntled ex-planet) • Millions of Comets
The Hazard • It’s all about Kinetic Energy • K = ½ mv2 • 10 m block @ 30 km/sec = 100 Kt • Multiply size by 10, multiply K by 1000 • Comets (large v) have more energy
The Impact Process • Atmospheric Entry • Contact-Compression • Penetration – Transient Crater • Excavation • Collapse
Comets and Planetary History • Superposition • Crater Saturation • Crater Degradation
Recognizing Craters on Earth • Craters rapidly destroyed by erosion • Circular geologic structures • Impact melts • Impact breccias • Shock metamorphism • Shatter cones
How Did The Moon Form? • Co-Creation • Fission • Moon should orbit in Earth’s equatorial plane • Capture • Can account for plane of Moon’s orbit • Very hard to do in reality • Collision • Requires no skill at all