Lecture 12 - Things Go Boom Flashcards
When and how was the universe created?
14 billion years ago, through the big bang
How is the life span of a star impacted by it’s size?
The bigger the star, the shorter the life span
- the sun is relatively small, 10 billion year life span
Supernova?
Signals the death of a star
Solar nebula?
A flattened rotating disk of hydrogen and helium dust, what formed the sun
How were the planets formed?
After formation of the sun, orther particles were trapped in orbits attracted other particles until they condensed to form the planets and other objects orbiting the sun
Asteroid?
10m-1000 km in diameter, consist of rock, metallic material, or a mix
Meteroid?
Smaller pieces of asteroids between dust sized and a few metres across
Meteor?
A meteoroid that has entered the earth’s atmosphere, emitting light as it moves
Meteorite?
A meteor that strikes the earth
Comet?
A rocky core surrounded by ice and covered in dust, has a glowing tail of gas and dust
What velocity do extraterrestrial objects enter the atmosphere?
12-72 km/s
Airburst
When an extraterrestrial object explodes in the atmosphre
Impact
When an extraterrestrial object hits the earth
What does an impact crater look like?
- bowl-shaped depression, upraised rim
- rims have an ejecta blanket
- broken rocks cement together into breccia
What makes impact craters different than other craters
- involve high velocity and high temperatures
- sends a shock wave, compresses, heats, melts, excavates rock
Why are impact craters more common on the moon?
- most impact sites on earth are in oceans
- impact craters on land have been eroded or buried
- smaller objects burn up and disintegrate in earth’s atmosphere
What is a simple impact crater?
small (a few km in diameter), do not have an uplift centre
What is a complex impact crater?
larger, can be 100 km, rim collapse, the centre of the crater floor rises following the impact
- most impact craters on earth that are larger than 6km are complex
What is a mass extinction?
the sudden loss of large numbers of species of plants and animals, classified when >20% of marine genera becomes extinct
How many mass extinction events have there been?
5 in the Phanerozoic
- L. Ordovician
- Devonian
- Permian
- Triassic
- Cretaceous (k)
What caused the first two extinctions?
global cooling followed by rapid warming
What cause the third extinction?
volcanic activity
what caused the fourth extinction?
impact of a large asteroid (on the K-T boundary)
the fifth extinction is linked to what?
cooling and glaciation
What is the 6th extinction event?
RIGHT NOW! because of global warming
How did scientists determine the extinction was caused by an impact?
Iridium in clay layers at the KT boundary, fossils below it weren’t found below
Where does iridium come from?
Iridium is found in asteroids, meteorites, and in earth’s mantle.
Where and when was the KT impact crater found?
1991, the Yucatan Peninsula (30-40km deep)
When does an asteroid become a problem?
When it’s path is disrupted by collision, and it leaves the space between jupiter and mars and heads for earth
Spaceguard program?
Study near earth objects with a diameter larker than 1km
What are our options if a near earth object is on a collision course with earth?
- intercept and blow apart - bad idea
- divert the path of the object - using explosions, much better
