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When a meteor hit the surface of a planet, it creates an impact crater. When an meteor hit the surface of a planet at an angle, like it usually happens in the movies, what do you call the long "ditch" that is formed before the actual crater where the meteor came to rest?

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  • $\begingroup$ I'm not sure what you mean in real life - something like these pictures of the Messier Craters? $\endgroup$ – Andy Sep 6 '16 at 17:32
  • $\begingroup$ @Andy I believe anber talking about the "tail" of a crater you often see in movies and tv shows. A good example would be this image from the movie Armageddon. $\endgroup$ – zephyr Sep 6 '16 at 17:47
  • $\begingroup$ @zephyr that is correct. Here is another example: i1.wp.com/guardiansofgeek.com/wp-content/uploads/2014/12/… $\endgroup$ – anber Sep 6 '16 at 17:50
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    $\begingroup$ Good question, and good answers (so far). To show that even impacts at an angle tend to create round craters, take a tray filled with a few centimeters of flour, springle cocoa powder on top, and throw pebbles at various angles; the craters are all quite round. And the flour creates long spikes easily visible against the cocoa, not unlike those seen on the Moon. It's a great experiment with kids (although pretty messy). $\endgroup$ – pela Sep 6 '16 at 18:26
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I think the answer to this is that it doesn't have a name because such "ditches" don't occur for real meteor impacts. In movies and tv shows, these ditches are often shown as being caused by the meteor first hitting the ground at some angle, then sliding across the ground, digging out a ditch along the way, until they come to their final resting point where the crater is.

When you stop to think about it, this scenario doesn't really make sense. These types of images (e.g., this one or this one) usually show a thin tail or ditch where the meteor first impacts which gets wider and deeper as the meteor scrapes on the ground, resulting in a final, large crater. But, the most energy a meteor imparts to the ground comes from the first instance it hits. If it were to scrape along the ground as portrayed in many movies, the crater would come from the point it hit the ground and the tail would be in the direction the meteor was traveling. The "ditch" or "tail" would get thinner and shallower as the meteor lost energy scraping across the ground. Generally the opposite is shown in movies.

But all that is moot anyway because meteors don't scrape along the ground at impact. That would just violate conservation of momentum and energy. You really have one of two scenarios.

  1. The meteor hits the ground with such force and energy that it mostly destroys itself and you wind up with just a crater. Such an example is the meteor crater in Arizona - in a stroke of brilliance called Meteor Crater. I would hazard a guess that almost all meteor impacts are of this form, be it on Earth or elsewhere.

enter image description here

  1. The other option is that the meteor isn't destroyed when it hits the ground. In this case, rather than dragging or scraping on the ground, your meteor will skip like a rock on water and create another crater on its second impact. In theory, it will keep skipping until it is finally destroyed or runs out of energy. This scenario requires that the impacting meteor is hitting at a very shallow angle with very little force and generally means that it is hitting a smaller body (but larger than itself) such as an asteroid/comet/moon. An example would be the Messier Crater on the Moon, linked by Andy in his comment. These types of craters are unlikely though, as they require pretty specific conditions to occur.

enter image description here

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    $\begingroup$ "Generally the opposite is shown in movies." - relevant to just every science topic ever. "That's not how it works!" "No, but that's how Sarah thinks it works, and we want her money." $\endgroup$ – corsiKa Sep 7 '16 at 1:18
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They considered a type of crater. If you dislike the word crater, you could describe it as an elongated impact structure.

These are known on the Moon and Mars, but are rather rare. On the Earth, an impactor at a lower angle will have to travel through a lot of air before reaching the ground. Making it more likely that the impactor will be broken up, and destroyed in the air, and so not form a crater.

Elliptical craters are known on Earth, such as the Matt Wilson Crater Or the debated Rio Cuarto craters.

Even in very shallow impacts, you won't get "ditch" being dug. That is only for the movies.

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  • $\begingroup$ I accept that impacts at an angle are not a realistic or common occurrence but if there was such a case, if I were standing in the "ditch" leading up to a crater, would I already be in the crater or is that called something else? $\endgroup$ – anber Sep 6 '16 at 23:19
  • $\begingroup$ I'll accept that it doesn't have a name. However, Lee Gildemeester's answer shows that writers have struggled describing this as well although not specific to meteors. $\endgroup$ – anber Sep 6 '16 at 23:30
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This isn't scientific, but in Ringworld by Larry Niven, a spaceship crashes at an angle that produces your 'crater'. The wording used by Larry Niven is:

"We are in a furrow plowed by our own landing."

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    $\begingroup$ I like the word "furrow". It may explain it perfectly but as mentioned, probably won't really show up in real meteor impact sites. $\endgroup$ – anber Sep 6 '16 at 23:33
  • $\begingroup$ The spaceship had a nearly indestructible General Products hull, protected during the impact by an actually indestructible stasis field. And it carved a furrow in scrith, yet another form of unobtanium. $\endgroup$ – Keith Thompson Sep 9 '16 at 5:44
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Whilst it is admittedly not a scientific text, here's a quotation from the 1977 novel Lucifers Hammer by Larry Niven and Jerry Pournelle:

"Dr. Sharps says that all craters are circular." Harvey posed above the cake pan with a lug nut in his fingers; he let it drop. Flour sprayed. "Whatever the velocity or the mass or the angle of flight of a meteor, it leaves a circle. I think he's right.

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  • $\begingroup$ The problem is that it's nonsense, not that it's not a scientific text. If Harvey had, instead, thrown the lug nut at an angle, it would obviously have made a non-circular mark. At this point, we would be forced to conclude that either there are lots of non-circular craters, or lug nuts and trays of flour are a bad simulation. $\endgroup$ – David Richerby Sep 7 '16 at 9:09

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