Turtle Back Rock

[ThatRoyGuy]

Just an interesting note for all of us who have visited Turtle Back Rock cache in NJ's South Mountain Reservation. Strange but apparently true, the turtle-back "carvings" on the rocks are actually natural formations! I spoke to a naturalist at the Turtle Back Zoo a day after visiting the cache, and he told me they are the result of quickly cooling magma in the area. Hard to believe for those of us who have seen it, but this guy seemed to know what he was talking about.

 

"No matter how cynical you become, it's never enough to keep up." - Lily Tomlin

[+The BeeGees]

Stayfloopy also told me it was from cooling magma. I had my doubts at the time but I guess that confirms it. Whatever it is, it looks pretty neat.

[BassoonPilot]

I had read that too, even before visiting the site. The thing that struck me as odd was that there is much evidence of glacial gouging and scraping in the area, but I didn't notice any on the patterned rocks.

[+orange]

That may be true but still I find it hard to believe.

 

Even smaller boulders seemed to have the pattern all around them. Now how did that happen? A round rock with same pattern all over it?

 

Me thinks I need to go back for a second look.

[+The BeeGees]

There are 3 things that bother me about the cooling magma theory.

 

1 - All of lines are the same diameter. I would think they would vary a little

 

2 - Very few of the cracks in the boulders occur in one of the etched lines. I would think these would be the weakest points and the first to fracture.

 

3 - If the lines are from cooling magma, how do they occur on several sides of a boulder or rock wall?

 

On the other hand, if they were carved, it should would have taken a long time. Those lines are everywhere.

[mortonfox]

quote:

---

Originally posted by The BeeGees:

There are 3 things that bother me about the cooling magma theory.

 

1 - All of lines are the same diameter. I would think they would vary a little

 

2 - Very few of the cracks in the boulders occur in one of the etched lines. I would think these would be the weakest points and the first to fracture.

 

3 - If the lines are from cooling magma, how do they occur on several sides of a boulder or rock wall?

 

On the other hand, if they were carved, it should would have taken a long time. Those lines are everywhere.

---

 

I also posted an explanation of the phenomenon way back when on... I believe... Team Excession's Washington Rock cache. Next time, I'll have to remember to also add the URL where I got the information to my log. I can no longer find my original reference via a google query.

 

There is no problem with the lines being the same length if the rate of cooling was uniform across the surface. But I suspect there is some variation. I just haven't gone there with a ruler to measure the lines.

 

Also, the lines are not the basalt itself but hardened minerals deposited in the cracks of the basalt. The basalt has since been eroded away. The lines, being hardened minerals, are not the weakest material in the rock so fractures need not always form there.

 

For point 3, I think we need a geologist.

[mortonfox]

quote:

---

Originally posted by The BeeGees:

There are 3 things that bother me about the cooling magma theory.

 

1 - All of lines are the same diameter. I would think they would vary a little

 

2 - Very few of the cracks in the boulders occur in one of the etched lines. I would think these would be the weakest points and the first to fracture.

 

3 - If the lines are from cooling magma, how do they occur on several sides of a boulder or rock wall?

 

On the other hand, if they were carved, it should would have taken a long time. Those lines are everywhere.

---

 

I also posted an explanation of the phenomenon way back when on... I believe... Team Excession's Washington Rock cache. Next time, I'll have to remember to also add the URL where I got the information to my log. I can no longer find my original reference via a google query.

 

There is no problem with the lines being the same length if the rate of cooling was uniform across the surface. But I suspect there is some variation. I just haven't gone there with a ruler to measure the lines.

 

Also, the lines are not the basalt itself but hardened minerals deposited in the cracks of the basalt. The basalt has since been eroded away. The lines, being hardened minerals, are not the weakest material in the rock so fractures need not always form there.

 

For point 3, I think we need a geologist.