hi I'm Diana and you're watching physics girl so I grew up in Hawaii on the island of Kauai which is the oldest of 18 islands the wettest the greenest the most beautiful it had no nightlife there were 22 kids in my graduating class look hi nigra so the Hawaiian Islands are geologically weird they're formed by volcanoes we know that but we describe that they're formed by a volcano just one it's like an upside-down chocolate kiss conveyor belt there's a hotspot that form of the volcano and then the plates move over the top making the islands one by one OOP now you know so one of my childhood friends Noah Randolph flag became a geologist at UC Berkeley and when we were back home over the holidays we went for a hike and got talking about how unusual the formation of the Hawaiian Islands is it all started with a mystery world war two US military was looking for Japanese submarines in the Pacific and the way they did that is they lower a magnet off the side of the boat and the magnet would get pulled down if there was a metal submarine under there the military mostly used planes with these magnetic contraptions but scientists later adapted the technology for both and well presumably they saw some submarines I don't know about that but what they also saw was the magnet would go up and down so periodically on the ocean floor sometimes would pull really hard and sometimes it wouldn't pull very hard you have a thought online this was a mystery this magnetic contraption was made in wartime to search for submarines underwater but something else was pulling on it something unidentified and deep underwater I'm going to guess that it had to do with how much magma was close to the surface of the ground and because there's more iron I'm guessing in that rock then it pulled harder you're totally right it's about yeah it's it well you're probably Noah's brother Jeremy who's also a geologist just told me that I'm not totally right you're totally right then it's about the iron in the rock if you imagine a molten rock as being a bunch of little magnets floating around what direction do you think those magnets would would align I was glad that they would align along the magnetic field lines xre okay so we have all of these magnets in the molten rock that align with the Earth's magnetic field yeah and then they freeze and they're stuck there oh okay go on and the Earth's magnetic field would reverse and so what they were seeing was these stripes was the reversals of the Earth's magnetic field and what yeah what yeah and the other thing they noticed is across the Pacific it's symmetrical it looks almost like a barcode yeah and but it's a symmetrical barcode and they're like well that means that that all that crust has been produced in the same place and this is how we learned that the earth even has plate it's the number one thing you learn in earth science tectonic plates and we figured it out because these lines and little magnets aligned with Earth's magnetic field as it flipped over millions of years and that was frozen into the rock amazing the vast majority of volcanic activity on earth occurs along plate lines and that makes sense because if you're going to spill your guts you're more likely to do it along a seam but there's one glaring exception why is dead in the middle of a plate plate tectonics doesn't explain in a place like away so that that's sort of a problem so what people call in is the sphere called mantle plume theory the idea right is so thermal convection is hot stuff is less than cold stuff is more dense cold stuff goes down hot stuff comes up so you imagine convection as the boiling of water on your stovetop right in the earth that convection is happening in solid rock yeah so we're talking about motion of solid rock right because at those timescales and at those length scales the ground the the solid rock that you feel is as viscous as the maple syrup that you're not amazing so this is rock moving through rock yes Wow so if you scale things the way that we think so they scale it looks like a lava lamp right you some hot stuff rising and it starts with a big blob and then there's this long skinny tail behind it the same physics happens in like nuclear bombs right here's a mushroom cloud it's the same idea right there's that big buoyant plume and then the tail the skinny tail behind so the idea is that Hawaii and the Hawaiian Islands and these other hotspot volcano to that tail hold on so this mantle plume theory says that an unusual hot spot like Hawaii is just the tail end of that blob shape of solid rock rising through solid rock that's it so then you might ask well where is big where's the bubble where's the bubble people have argued is that those bubbles are these things called flood basalt is this is good at commis this huge bubble just explodes onto the surface and so most of Siberia is covered in lava flows and most of India is covered in lava flows individual lava flows that are hundreds and hundreds of feet tall that cover an entire country Wow and that was I mean I like a thought exactly a bubble level exploding yeah I've had a bubble exploding into the surface this is the tail in that the head and then as the head gets higher and higher the pressure is released and that means that the solid rock is going to start turning from a solid into a liquid yeah and so that's what we that's what we call magma and the reason we are calling anything like that have never never would it be an incredibly violent event well this gets good there's been many extinctions in Earth history and many of them correspond with when we think these bubbles explode to the surface so the most recent one was 40 million years ago and it was tiny like a thousandth of the size of some of these yeah but the the largest extinction or history the perma Triassic happens during the largest flood default so yeah let's hope that doesn't happen anytime soon okay so recap the Hawaiian Islands are forming on a hot spot that's the result of one of these massive plumes popping up through the crust like a hot container you're welcome and this might tell us something about the geology on the planet Mars we think that plate tectonics is not happening on Mars but we think that probably mantle plumes are and that's why we have the giant volcano like olympus mons and part of why olympus mons is so big is because there's not plate tectonics okay so that's sort of piling up in the same place but in Hawaii because the plate is moving you get snapshots it's exactly like how your video camera works right if you're taking a series of Stills and you can see the progression through time and so what we see in the Hawaiian chain is a series of still of the island through time so when you go to the big islands that's it's being born and then you can trace that chain of islands to here which is five million years and you can trace it all the way all the way up to up to Siberia yeah you go that is the line of them like the motion of plates over that one yes do me a favor go to Google Maps or Google Earth and pull up some Hawaiian Islands maybe after you finish watching this video trail satellite view and you'll see a line of old mountains traced by the same hot spot all the way up to Siberia it's incredible and you'll notice the line is crooked which means that at some point the plate just change direction which is weird but crazy that you can tell something like this about history from looking at the ocean floor so you can take the distance between the Hawaiian Islands we actually know the ages and you can calculate velocity and those are the same velocities that we measure with GPS is now exactly that yeah that's really cool so there's a lot of stuff we're still learning about the Hawaiian Islands thanks to NOAA for trying to quench my unquenchable curiosity thanks to you for watching subscribe if you want more physics or whatever we decide to get physical with and [Music] just kidding how because I think that [Music] was awesome yes