Meteors! (was: René-Levasseur Island)

Boyd

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This otherworldly topographic feature really jumped out at me when I made my new North America map, was not aware of it before - it's about 40 miles in diameter.

https://boydsmaps.com/#9.78/51.392008/-68.672812/mbx3dnalc/0.00/0.00

René-Levasseur.jpg

Here it is on the Canvec Topo Map.

https://boydsmaps.com/#10.00/51.392008/-68.672812/toporama/0.00/0.00

And it's just what it looks like!

"The geological structure was formed by the impact of a meteorite 214 million years ago. The meteorite is believed to have been about 5 km in diameter, and would have hit Earth at a speed of 17 km/s, the fifth most powerful known impact that Earth has seen. The impact of the meteorite formed a crater roughly 100 km in diameter, the centre of which forms the island known today."

 
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Boyd

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Here's another one I hadn't noticed before - Lac L'Eau Claire (Clear Water Lakes)

https://boydsmaps.com/#9.65/56.210355/-74.503713/mbx3dnalc/0.00/0.00

clearwater.png


"About 290 million years ago, two large asteroids smashed into Earth. The massive craters they left behind—now lakes—are still visible from space.
When they struck, the binary asteroids crashed into a part of Earth’s crust that was fairly close to the equator. Since then, millions of years of plate tectonics have pushed the craters north into what is now northwestern Quebec."



Canvec topo map

https://boydsmaps.com/#11.00/56.210355/-74.503713/toporama/0.00/0.00
 
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bobpbx

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I love info like this. I have National Geo's from the 20's, 30's 40,s and so on up this centery. Not all, but several hundred. There is (If my memory serves me) another one further north that I read about....in Natl Geo some scientists visited it. Here's a video I think about the one you posted.

 
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Boyd

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There is (If my memory serves me) another one further north that I read about

Good tip! My map really makes the craters stand out - I just scrolled North and found it - Lake Couture

https://boydsmaps.com/#11.00/60.126333/-75.295607/mbx3dnalc/0.00/0.00

couture.png


"Most of the lake covers an 8 km in diameter impact crater. The crater is estimated to be 430 ± 25 million years old (Silurian). Breccia, suggesting impact origin, is present in boulders at the surface on islands around the perimeter of the lake"


Topo map

https://boydsmaps.com/#12.00/60.126333/-75.295607/toporama/0.00/0.00

Here are a couple interesting sites that I found with information on more craters, have not taken the time to read through them yet.


 
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Boyd

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Looking at those links, this appears to be the closest crater to NJ. Nothing to see on the map however.

 

bobpbx

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That is so mind-blowing. From the Chesapeake article: "Tropical rain forests covered the slopes of the Appalachians."

Not many people know that (I read this, but I'm 'pretty' sure its correct) the slope of the Appalachian chain slides beneath New Jersey, even in South Jersey. Drill down beneath the sand far enough and "CLANG!", the drill bit hits granite (or some other hard rock).
 
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stiltzkin

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As a kid, I had always heard that the Blue Hole was made by a micro-meteor impact, but I think this is pretty firmly in Jersey urban legend territory.

As far as actual impact sites, Toms Canyon crater is about 100 miles east of Atlantic City and is probably the closest one to us. It is probably geologically related to the Chesapeake Bay impact that was already mentioned. Not much to see after 35 million years, even on bathymetry maps.
 
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Boyd

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As a kid, I had always heard that the Blue Hole was made by a micro-meteor impact, but I think this is pretty firmly in Jersey urban legend territory.

Yeah, I think that has been de-bunked. But Beck's chapter about the Blue Hole was entitled "Maybe a Meteor?" (IIRC).

That is so mind-blowing

Also mind-blowing that the Clear Water Lake impact originally occured near the equator, but the tectonic plates have shifted so much that it's now in Northern Canada!
 
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Looking at those links, this appears to be the closest crater to NJ. Nothing to see on the map however.



Do you see what I see?
 
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Boyd

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Looking at this... it is considerably smaller than the Canadian ones, it's about 2 miles wide. The Couture crater is about 6 miles, Clearwater craters are about 11 miles and 18 miles, Levasseur is around 40 miles.

This one is also raised above the surrounding land, unlike those flooded craters that are now lakes. I'm gonna guess it is the product of erosion. But this wouldn't be the first time I was wrong either. :D
 
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Boyd

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Well.. who am I to argue with Spung-Man? :D In that case, it's possible to visualize this as similar to René-Levasseur, which is a raised island surrounded by an annular lake. Here it is rendered with a local elevation shader to bring out details.

The blue/green creek/wetlands area from about 1:00 o'clock to 9:00 o'clock is like the annular ring. Then you have higher ground between 10:00 to 12:00, however I can imagine the ring continuing through the purple gap between higher areas at 10:00-11:00 o'clock.

meteor.jpg
 
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Well.. who am I to argue with Spung-Man? :D In that case, it's possible to visualize this as similar to René-Levasseur, which is a raised island surrounded by an annular lake. Here it is rendered with a local elevation shader to bring out details.

The blue/green creek/wetlands area from about 1:00 o'clock to 9:00 o'clock is like the annular ring. Then you have higher ground between 10:00 to 12:00, however I can imagine the ring continuing through the purple gap between higher areas at 10:00-11:00 o'clock.

View attachment 17874
I concur.
 
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Apr 6, 2004
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Well.. who am I to argue with Spung-Man? :D In that case, it's possible to visualize this as similar to René-Levasseur, which is a raised island surrounded by an annular lake. Here it is rendered with a local elevation shader to bring out details.

The blue/green creek/wetlands area from about 1:00 o'clock to 9:00 o'clock is like the annular ring. Then you have higher ground between 10:00 to 12:00, however I can imagine the ring continuing through the purple gap between higher areas at 10:00-11:00 o'clock.

View attachment 17874
Where did you get that wonderful lidar??
 

Boyd

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It's the same data and the same "spectrum" shader that I created for the 2022 3d LIDAR in the Pines map. If you zoom way out on that map, you'll see that the colors are the same. The shader has 36 colors that each represent 10 feet on the map of the pines. However, in the little image of the "crater", there is only an elevation range of 75 feet, so each color is representing ~2 feet. This makes the elevation changes much more obvious.

So all the bright colors are deceiving you, there is no "wonderful LIDAR", it's just the same data presented differently. But it highlights how these shaded relief maps work, they are more interesting when the range of elevation is limited.

I changed the title of this thread to better reflect the subject matter and am going to ping Mark to see if he can take a break from his scholarly pursuits long enough to share some wisdom. :)
 
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