Chapter 14: Impacts & Extinctions

Where are asteroids found?

In the asteroid belt between Mars and Jupiter

Define meteoroids

Broken up asteroids

Define meteors

Meteoroids that enter Earth's atmosphere (shooting stars)

Define meteorites

Meteors that hit Earth's surface

What is the speed that objects enter Earth's atmosphere?

7 to 45 miles per second

What is an airburst?

A meteoroid that explodes in the atmosphere

What was interesting about the Chelyabinsk airburst in 2013?

It was the largest known asteroid to enter Earth's atmosphere since Tunguska airburst in 1908

Why was the Chelyabinsk asteroid not observed before it struck the Earth?

Meteor astrophysicists were tracking a different asteroid

What was the most powerful natural explosion in recent Earth history?

The Tunguska asteroid, releasing energy equivalent to ~185 Hiroshima bombs

What are the craters on the Moon so well preserved?

The moon has no geological activity or erosion so craters are not erased.

Define mass extinction

Sudden loss of large numbers of plants and animals relative to number of new species being added

What are three possible triggers for a mass extinction?

1-plate tectonics

2-volcanic activity

3-meteorite impact or airburst

How many major mass extinctions have occurred?

Six

During the Great Permian Extinction ___% of all vertebrate species on land and ___% of marine organisms were destroyed

70%

90%

What is the possible cause of the Great Permian Extinction?

Large basaltic volcanic eruptions in Siberia

What animal thrived after the Permian Extinction?

Reptiles

What is the Mesozoic often called?

"Age of Reptiles"

For how many years did dinosaurs rule the land?

180 million years

How long have the modern form of humans been around?

200,000 years

Besides dinosaurs, what other organism ruled during the Cretaceous Period?

Giant crocodiles

It is estimated that ___ of all plant and animal species went extinct at the end of the Mesozoic

3/4

What is thought to have caused this extinction?

A large meteorite strike at the Yucatan Peninsula 65 million years ago

What evidence is there for an asteroid collision 65 million years ago?

1-cm thick layer of sediment containing high level of iridium

What is the shorthand for the Cretaceous-Paleogene boundary?

K-Pg (used to be termed the K-T boundary)

How big was the crater in the Yucatan peninsula?

125 miles in diameter and 25 miles deep

What were some of the devastating effects of this impact?

-dust and debris blocks sunlight

-sulfuric acid enters atmosphere

-fireball sets off wildfires around the globe

-tsunamis reach over 1000 ft high

What is happening on Earth one month after the impact?

-there is no sunlight and no photosynthesis

-acid rain

-food chain has stopped

What is happening on Earth several months after the impact?

-sunlight returns

-acid rain stops

-ferns restore burned landscape

How often do impacts of this size occur?

Once every 40 to 100 million years

In the Cenozoic ___________ replace the reptiles as dominant vertebrate life forms on land

mammals

In the Cenozoic mammal groups became very large. What are some examples of these large mammals?

-wooly mammoths

-giant ground sloths

-saber toothed tigers

What is special about the La Brea Tar Pits in Los Angeles?

The tar pits trapped over 650 species of Ice Age animals such as the mammoth, plus one human skeleton

When did the Pleistocene epoch end?

11,000 years ago

What was the climate like in the Pleistocene?

Warmer as evidenced by the ice sheets and glaciers receding

What recent theory explains the disappearance of large Pleistocene mammals and the Clovis people 12,900 years ago?

An airburst caused intense wind and wildfires that destroyed forests and grasslands. The atmosphere was polluted with soot and toxic fumes.

What are ways to minimize hazards from an asteroid impact?

-blow it up in space

-nudge it out of Earth's orbit

-evacuation of impact point

What are some other theories on what wiped out the large mammals of the Pleistocene?

They were hunted to extinction, or climate warming at the end of the Ice Age weakened them.

What epoch began at the end of the Ice Age and continues to present day? (Hint: it follows the Pleistocene)

The Holocene epoch