How long does it take lava to cool?

Question

How long does it take for lava to cool to the point that it can be walked on barefoot?

Answer 1

You've asked a good question, If it is pahoehoe lava (the smooth glassy type) it will support your weight after only 5-10 minutes since it stops moving. It will still be pretty hot and uncomfortable, and probably might melt your boots, but if you absolutely had to get across such a flow you could. 'A'a flows are a different story. They are the big rough-surfaced flows with a top surface made up of broken and spiny blocks called clinkers. You can walk on an 'a'a flow while it is still moving but it is not very pleasant. 'A'a is not very fluid so you don't have to worry about sinking in but because there are so many spaces between the clinkers for heat to escape, they are really hot. You would only cross a hot one if you absolutely had to.
There is an account in the Lyman Museum in Hilo that says that the old Hawaiian Kahuna (priests) would step on fresh pahoehoe toes so that the molten lava would squish out the sides, just to impress the common people!

lava, cools at different rates depending on how fast it is flowing. If it is flowing really fast, every time a cool crust develops, the motion of flowing breaks it apart and it has to form new crust. The new crust gets broken again, and on and on and on. All the broken pieces of crust are jagged and rough, and form the top layer of the flow. These are called 'a'a flows. Because 'a'a flows tend to be pretty thick (2-10 meters), their interiors cool very slowly once the flow comes to rest. An `a`a flow may be still warm a couple of weeks after it has stopped (as long as it hasn't been raining heavily. Only when the flow pretty much stops does it really begin to cool. When lava is flowing slowly, it can form a crust that gets carried along with the flow. In this case the crust is smooth and glassy, and this type of lava is called pahoehoe. Pahoehoe flows are made up of thousands of small flows called "toes" A single pahoehoe toe will be hard enough to walk on in about 20 minutes, and pretty much cooled in a couple of days. The thing is you never have just one toe, you have a whole pile of them so put together they will cool much more slowly. If the whole flow is 2-5 meters thick it can take just as long as an 'a'a flow to completely cool.

Pahoehoe and 'a'a are Hawaiian words that have been adopted by volcanologists all over the world. They don't have any other meaning other than the names of these types of lava. There are some stupid books that say "'a'a is what ancient Hawaiians used to say when they walked on 'a'a lava barefoot." This is a racist remark that has no basis in fact. Hawaiians were not so stupid that they would walk on 'a'a barefoot. Other equally stupid books say that "pahoehoe" means ropy or satiny in Hawaiian but that is not true either. They are just names for these types of lava.

Answer 2

Wouldn't that depend on how much lava you're dealing with, and other conditions such as weather & wind? A very thick layer would probably take a long time to cool, while a layer barely covering the ground underneath would cool down quickly... and windy conditions or rain would cool it down quicker too.

Answer 3

It would depend on where it was flowing and the environment. If it rained, snowed or was in a very cold climate it may cool faster....

Answer 4

Do your work for your self and use a book

Answer 5

I'm gonna say 2 days

Answer 6

Not too sure - but I wouldn't be the first one to test it , if I were you .