2985: Craters

2024-09-15T12:07:37Z

Aetheraev: /* added the word structure to clarify that stonehenge is not a single megalith */

{{comic
| number = 2985
| date = September 13, 2024
| title = Craters
| image = craters_2x.png
| imagesize = 457x352px
| noexpand = true
| titletext = It's annoying that the Nastapoka Arc isn't a meteor impact crater, but I truly believe that--with enough time, effort, and determination--we could make it one.
}}

==Explanation==
{{incomplete|Created by a LITTLE PRINCE ON A ROCK - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic uses a Venn diagram to classify large circles on the ground into meteor impact craters, "weird circles on the map", and both.

{| class=wikitable
! scope="col" | Venn diagram section
! scope="col" | "Crater"
! scope="col" | Explanation
|-
|rowspan="4"|Meteor Impact Craters || Northern {{w|Yucatan Peninsula}}|| This refers to the famous {{w|Chicxulub crater}}, where an asteroid ~10 km in diameter struck the Earth 65 million years ago and caused the extinction of non-avian dinosaurs.
|-
|{{w|Charlevoix impact structure|Charlevoix Region}}|| Astroblème de Charlevoix, or Charlevoix impact crater. A 400 million-year-old, 54 km-wide crater which lies partly in the waters of the {{w|St. Lawrence River}} and stretches halfway between {{w|Quebec City}} and the mouth of the {{w|Saguenay River}}.
|-
|{{w|Sudbury Basin}}||A large valley in Ontario, formed by an impact 1.849 billion years ago.
|-
|{{w|Chesapeake Bay Impact Crater|Chesapeake Bay}}||A crater buried beneath the mouth of Chesapeake Bay, where an impact occurred around 35.5 million years ago.
|-
|rowspan="4"|(Venn diagram intersection)||{{w|Manicouagan Reservoir|Lake Manicouagan}}||A large ring-shaped lake in Quebec, formed about 214 million years ago.
|-
|{{w|Lonar Lake}}||A circular lake in the Deccan Traps basalt of India, formed approximately 570,000 years ago.
|-
|{{w|Clearwater Lakes}}||A pair of lakes next to each other in Quebec, one formed 460-470 million years ago, the other formed closer to 286 million years ago.
|-
|{{w|Meteor Crater}}||A crater in Arizona about 1.2 km across where a meteor hit around 50,000 years ago.
|-
|rowspan="5"|Weird Circles on the Map||{{w|Nastapoka Arc}}|| A section of the shoreline of southeastern Hudson Bay that's almost a perfect circle.
|-
|{{w|Crater Lake (disambiguation)|Crater Lake}}||Most likely reference is the {{w|Crater Lake}} that's in Oregon, the deepest freshwater body in the United States, which formed in the {{w|caldera}} of {{w|Mount Mazama}} after it exploded around 7700 years ago.
|-
|{{w|Stonehenge}}||{{w|Stonehenge}} is a {{w|megalith}} structure on the {{w|Salisbury Plain}} in England which is famous not only for its historical significance and impressive scale but for {{w|Theories about Stonehenge|stories surrounding its creation and purpose}}.
|-
|The {{w|Great Blue Hole}}||A large, nearly-circular {{w|Blue hole|marine sinkhole}} off the coast of {{w|Belize}}.
|-
|{{w|Twelve-Mile Circle|Delaware's northern border}}||The {{w|Twelve-Mile Circle}} comprises several surveyed arcs that define the borders between {{w|Delaware}} and {{w|Pennsylvania}}, and between Delaware and bits of {{w|Maryland}} and {{w|New Jersey}}. These arcs and Stonehenge are the only manmade features in this comic.
|}

The title text refers to the {{w|Nastapoka Arc}}, a section of the Hudson Bay shoreline that is almost a perfect circle. This was most likely caused by continental plates crashing into each other rather than a meteor impact. However, Randall believes that it CAN be an actual meteor impact site with enough dedication: he wants to redirect an asteroid into Hudson Bay, which is a bad idea{{Citation needed}}. There is no efficient way to artificially direct asteroids towards Earth, let alone ones large enough to make the appropriate size hole. The {{w|Double Asteroid Redirection Test}} (DART) slightly changed the orbit of one asteroid around another by slamming a spacecraft into the asteroid; doing any more substantial redirection would require applying large {{w|Impulse (physics)|impulse}} to an asteroid, which has never been done. Moreover, the precision required would be a massive obstacle: a small variance in timing or angle would make the asteroid hit Earth in the wrong manner, at the very least creating an improperly matched hole (for size and shape), with the most likely outcome being to miss the original feature entirely. There is also the potential to slam into nearby populated areas, but some historic circular features are {{w|Nördlingen|themselves populated}} so would suffer directly in the case of a perfect impact. Attempting to do so would be costly{{Citation needed}} and potentially cause massive devastation.{{Citation needed}}

This idea of directing an asteroid to directly impact the Earth is on some level an inversion of disaster movies like ''Armageddon'', where an asteroid is landed on to destroy or deflect it. ''Armageddon'' has been discussed before on xkcd.

==See also==
{{w|List of impact structures on Earth}}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[A Venn diagram with two circles.]
:[Label above left circle:]
:Meteor Impact Craters
:[Label above right circle:]
:Weird Circles on the Map
:[Left circle items (Meteor Impact Craters):]
:Northern Yucatan Peninsula
:Charlevoix Region
:Sudbury Basin
:Chesaspeake Bay
:[Right circle items (Weird Circles on the Map):]
:Nastapoka Arc
:Crater Lake
:Stonehenge
:The Great Blue Hole
:Delaware's Northern Border
:[Middle intersection items:]
:Lake Manicouagan
:Lonar Lake
:Clearwater Lakes
:Meteor Crater

{{comic discussion}}

[[Category:Venn diagrams]]
[[Category:Geology]]
[[Category:Geography]]

explain xkcd - User contributions [en]

2985: Craters