Earth’s Known Impact Structures Earth retains the poorest record of impact craters amongst terrestrial planets Why?Plate tectonics - Erosion – Sedimentation - Life Oceans are relatively young and hard to explore Many impact structures are covered by younger sediments, others are highly eroded or heavily modified by erosion.Few impact craters are well preserved on the surface ~160 Manicouagan, Canada (62mi) Roter Kamm, Namibia (1.6mi) Brent, Canada (2.4 mi) Wabar, Saudi Arabia (0.072mi) Vredefort, South Africa (125-185mi) Meteor Crater, AZ (0.75mi) Wolfe Creek, Australia (0.55mi) Spider, Australia (8.1mi) Popigai, Russia (62 mi) Meteor Crater a.k.a.

dating terrestrial impact structures-67

Less than 1 mile across, it was created about 50,000 years ago. Lots of melted droplets and solid pieces of an iron-nickel material have been recovered in the area.

First-recognized impact crater on Earth: Meteor Crater 1891: Grove Karl Gilbert organizes an expedition to Coon Mountain (old name of Meteor crater) to explore the impact hypothesis.

He soon concluded that there was no evidence for impact, and attributes it to volcanism.

1902: Daniel Moreau Barringer secures the mining patents for the crater and the land around it.

1906 & 1909: Barringer writes papers attributing the crater to an impact event.

Drilling and exploration continued at great expenses.

1928: Meteor crater becomes generally accepted as an impact crater.

An article from National Geographic attributes the impact hypothesis to Gilbert, and fails to mention Barringer’s work.

1929: Investors decline to provide more funding to continue drilling. 1946: The crater becomes officially “Meteor Crater”.