impact craters

Question 1

what are the three stages of impact cratering

Answer 1

compression
excavation
modification

Question 2

what is the compression stage of impact cratering?

Answer 2

• shock wave expands out from point it hits / point of impact
• compressed rock to 1/3 usual volume
• some rock melts, some rock fractures, and you get a rock that flows like a fluid to create a hole / crater
• the point where the shockwave comes out is below the surface, so it penetrates into the surface and then evaporates
• pushes down, the out, then up

Question 3

what is the excavation stage of impact cratering?

Answer 3

• decompression wave follows the advancing shock
• ejecta: travels out as conical sheet
• transient cavity
• some stuff falls back into the crater
• crater rim is overturned

Question 4

what is the modification stage of impact cratering

Answer 4

• large structures
• gravity cannot sustain cavity
• slump crater wall
• central uplift
• planet trying to fix / fill the hole
• impact melt

Question 5

how many impact events are recorded in the Earth’s crust?

Answer 5

200

Question 5

what are some features of the impact cratering process?

Answer 5

ejecta blanket
overturned rim
impact melt sheet
central uplift sometimes (peaks or rings)

Question 6

what are the global effects of the chicxulub impact event?

Answer 6

• tsunami was nearly global, with 10m high waves
• equivalent of magnitude 10 earthquake
• melted target rock fell back to earth for 3 days, sparking wildfires
• soot from fires prevent photosynthesis for 18 months
• 75% of all plant and animal species went extinct
• ejecta clustered in gills of fish

Question 7

how did the chicxulub impact event effect life on earth in the future

Question 8

how is humanity looking out for civilization-ending impactors?

Question 9

what is a transient cavity?

Answer 9

maximum excavation, bowl shape, deepest it goes, resistance to material it hits

Question 10

what is breccia from the impact crater process?

Answer 10

jumble mess of rock fragments, glass, sand, minerals, other stuff from melting, breakage, and sediment of material

Question 11

what is tektites from the impact crater process?

Answer 11

bits of glass, the target rock (piece of the earth crust) melts, and droplets of melt ejected up and fall back down to the ground

Question 12

what is the difference between a simple and complex crater?

Answer 12

simple crater: smaller structures that impact
complex crater: larger structures that impact

Question 13

what determines the size of a crater?

Answer 13

gravity dependent

Question 14

what makes an asteroid more likely to hit earth

Answer 14

smaller diameter, higher number of them exist

Question 15

sand and dust events occur?

Answer 15

daily

Question 16

meteor and fireball events occur?

Answer 16

yearly

Question 17

is an impact event a hazard or a risk?

Answer 17

hazard

Question 18

what are the two types of hazards?

Answer 18

anthropogenic: environmental change influenced by people (war, global warming, famine)
non-anthropogenic: environmental change not influences by people (pandemic, solar fire, volcanism, impact)

Question 19

what are the major hazard according to the doomsday clock?

Answer 19

• nuclear security
• climate change
• biological threat (pandemic)
• disruptive tech in age of disinformation
• anthropogenic

Question 20

what are the three ways we can mitigate the risk of impact?

Answer 20

1. observe: more we can identify PHAs and determine their orbits
2. plan: over 10 exercises involving hypothetical simulation
3. prepare: develop technology to deflect a PHA (NASA DART mission)