What crashed into earth?

Answer 1

In the Late Heavy Bombardment, about 500 million years after the formation of the Earth, (or what passed for it in those days) a planet Theia, about the size of Mars crashed into Earth. [it may have been Mars?] both were well destroyed and re-assembled themselves.

There are still traces of other giant circular features on the surface of the Earth, but these are almost certainly more modern. But some mineral deposits in the US coincide where these features intersect.

The Sudbury Crater in Canada, a rich source of nickel is a bolide crater about 200-250 km diameter. 1844 million years ago. Bolide 10km? diameter.

In 1960, F van Der Hoeven and others, left Scott base and traversed the Victoria Land in Antarctica, and by gravity anomalies inferred the location of a group of bolides which landed in Antarctica about 780 000 years ago. This bolide field is many hundreds of km in size. This melted a LOT of ice and raised the level of the Oceans about 60 cm. This magnetic anomaly coincides with the latest magnetic reversal of the Earth, and the location more recently confirmed by satellite measurements.

About 65 million years ago a bolide crashed into the Earth at Chicxulub on the Yucatan Peninsula. This bolide wound have been approx 10km in diameter, and landed at an angle of 20o - 30o. This wiped out many genera of life forms, and the survivors on land were able to shelter (and hibernate?) in the holes in the ground. Known in geological circles as the K/T Boundary, and recognized world wide by an iridium anomaly of about 500 ppb, as compared with ~3ppb in the Earth's crust. [ppb = parts per billion]

The sharks had a good time, as did many ocean dwellers, but we lost the Ammonites.