Saturday is the day we mix two things that don’t go together. Today we have selected “Lava” the hot stuff, and “Water” the cold stuff!
(But last things first… We digressed into tongue twisters/volcanic ash and James Bond movies…so naturally I’m adding links to those discussions…)
First off is a crazy idea….Which one floats? When the density of one material is greater than the other, it will sink.
The one that is less dense will float!
Fresh water has a density of 997 kg/m³ and lava is 3100 kg/m3. (Salt Water is 1020 kg/m3).
So naturally water will float on top of lava. And lava pouring out of a volcano into the ocean will sink. We get this and it makes sense…. (David points out that the hot lava can boil the water and salts out of the ocean to make a toxic acid and even flying glass shards from the rapidly cooling lava! Go Earth! You win! )
If the lava traps the water and the water is superheated, then the results can be explosive!
Steam packs a mighty punch and can make for the explosive results we associated with the word “eruption”!
(These guys play with lava and water just for fun).
What about a human? Would we float in lava or sink? (Check here to see this from the point of view of a turtle!) All the cool movies show people sinking in lava. The Anakin Sky Walker sinking at the edge of the lava lake is the first image that comes to mind….
I’m an engineer so let’s answer this in the engineering way.
Humans have a density of about 985 kg/m3. This is slightly less than water and an even greater difference with salt water. This is why living humans usually float in salt water. (By the way, when you breathe in oxygen, your density changes to 945 kg/m3 and you float even a little bit higher….)
So what about lava? Would you float in lava or sink in lava? All the movies show people sinking into lava. That “feels” right to us. Because lava looks like a liquid, and it’s flowing, so we should sink right?
Well not unless you are the terminator and made out of something denser than human flesh! The math says that you will FLOAT on lava. (Never mind the obvious burning that will occur!)
But back to the original question…what happens when lava and water get together for a vacation?
The answer is “it depends”.
Sometimes the result is an explosive mixture of basalt glass shards flying everywhere. Sometimes it is fumes and toxic liquids.
The video on the left shows what is happening today in the Canary Islands as a volcano that was quiet for 50 years, springs to life pouring black lava through beautiful homes in what was once lovely neighborhoods.
Poignant, sad, tragic, and all the while a powerful testament to the constant recreation of the world.
Oh, and you also get to see lava mixing with pool water. Bet you never saw that before.
Back to our story folks.
The idea that lava can rip away our homes is a distant thought for most people, even here in Japan where we are surrounded by volcanoes and frequent rumblings of earthquakes.
That being said, the Hawaiian Islands were made by lava spewing forth from a crack in the earth’s crust. As the crust drifts westward toward Japan, the islands created from the lava are dragged with it. The current stability in our crust is shown by the size of the Big Island of Hawaii. The island there is still growing and sometimes even homes are absorbed in the new lava flows.
Thats’ the down side of a lava flow.
The upside can be seen here in Iceland!
This is a 2015 Post showing a brand new hot springs fed by magic lava and magic water!
That’s all for our recap. Click here for the offshoot of our digress topics!