There are a lot of interesting things about Hawaii. You can, and I did, go off on quite the chain of Wikipedia reads related to our nation’s 50th state. For today, though, I want to focus on the question which drove me to Hawaii’s Wikipedia page in the first place: Who put that there?
Conceptually, continents have made sense to me for a while, especially after seeing a time-lapse depiction once at a natural history museum of all the continents moving around from Pangaea to today. Islands, though, are more confusing—especially these particular islands, placed smack dab in the middle of the biggest ocean in the world.
It turns out that to explain how the Hawaiian Islands got there, you first need to make sure your audience has a basic understanding of plate tectonics. To get up to speed, we first need to explain plates.
The Earth’s crust is divided up into a bunch of pieces, which, when mapped out, look kind of like a broken dish being put back together. These pieces are called tectonic plates, and they’re responsible for a lot of how our land and oceans are shaped. I’ve included, below, a map of the 15 main plates. The reason they’re the “main” plates is because there are some smaller plates mixed in here, but they’re very small, and the existence/boundaries of some is the subject of scientific debate—the theory of plate tectonics is fewer than 70 years old, and while as a whole it’s widely accepted (which is why I’m presenting this as fact, rather than as just a theory, though as with anything, it’s possible we could all be wrong), the exact nature and borders of smaller plates are still being hashed out. Anyway, here are the main plates.
Feel like you understand what plates are?
Good, because this is about to get weirder.
These bad boys are moving.
Yes, if you see the red arrows on the map, you can see where plates are pushing against each other, pulling away from each other, and sliding against one another. When this happens quickly, there’s an earthquake (earthquakes can happen for other reasons, too, but that’s a matter for another blog post). There are also volcanoes along these borders between plates, which are called fault lines. That’s because fault lines, and the motion along them, create an opportunity for magma, the rock inside of the Earth that’s so hot and pressurized that it’s melted into liquid, to escape, shooting or bubbling up onto the surface of the Earth and becoming part of the Earth’s crust. The collisions of these plates give rise to mountains, and the separations between them create oceanic trenches. Plates are a big deal.
As you might have imagined, since some plates are pulling away from each other, plates are capable of growing. On the other end, they’re capable of shrinking. Plates change over time. The plates we currently see haven’t been around forever, and won’t be around forever. As individual humans, though, and as a species (I think?), these are the only plates we’ll ever see. That’s because these plates move really slowly. The Pacific Plate, for example, moves about 32 miles every million years, or one inch per every six months (on average).
Now that we’ve got that covered, let’s get back to Hawaii.
As you may have noticed, Hawaii is in the middle of the Pacific Plate. It isn’t along a border. Yet there’s land there, and there are volcanoes. What gives? Can scientists explain this?
They can!
It turns out there’s this thing they call a hotspot where magma sneaks through the middle of a plate. Why this happens is debated. Based on what I’ve read, it seems the theories range from there being a very hot area of the Earth’s mantle (that’s the layer right underneath the crust) to the crust just being a bit thin in some places.
Whatever, the case, one of the most notorious hotspots is the Hawaii hotspot, which has produced over 100 volcanoes in its illustrious career.
What seems to be happening is that the Pacific Plate is passing over the Hawaii hotspot. As it passes, magma escapes through the crust, slowly building itself into a volcano. The volcanic eruptions in the news at some point in 2018 on the Big Island (the island named Hawai‘i) were produced by this hotspot. So, chances are you’ve seen video of its performance, even if you’ve yet to see it live.
The Hawaii hotspot has been doing this for so long that its volcanoes stretch all the way to the edge of the Pacific Plate, comprising a partially-underwater mountain range called the Hawaiian-Emperor seamount chain. Here’s a picture (or a depiction—I’m not sure which):
In case you’re struggling to orient yourself, here’s a picture with some labels I added in Microsoft Paint:
Now, we don’t call all of this Hawaii, and not all of these are active volcanoes. After a while, the volcano gets so far from the hotspot that its magma supply gets cut off, and it’s left to erode. Eventually, it erodes so much that it isn’t visible above the sea level. Some, though, as in the case of Midway Island and a few others you might recognize, are still poking through.
There are five Hawaiian volcanoes that have erupted within the last 600 years. Haleakalā, which makes up three quarters of the island of Maui, last erupted between 1480 and 1600 A.D. Hualālai, on the western edge of the Big Island, last erupted over 1800 and 1801. Mauna Loa, also on the Big Island, last erupted in 1984. Kīlauea, also on the Big Island (the Big Island is made of five volcanoes in total), has been erupting continuously since 1983, in varying levels of intensity.
There’s one more volcano that’s liable to erupt in our lifetimes, though. It last did it in 1996, but it didn’t make much noise. That’s because it’s underwater, and one day, estimated to be 10,000+ years from now, it will be Hawaii’s newest island.
Its name is Lōʻihi, and right now, its peak is 3,000 feet below sea level. It’s growing, though. It’s potential impact in our lifetimes, by my inference, seems limited to earthquakes that can result from magma moving, as it does in a hotspot, but as we’ve established, it will one day be the newest Hawaiian island. Here’s a map of where it is right now:
It looks pretty close to the Big Island, right? I wonder if after it becomes its own island it’ll merge with the Big Island, or if the Big Island’s gonna erode first into littler islands. Also, why does the Hawaiian-Emperor seamount chain turn North as you follow it West?
So many questions. Those, though, are for further Wikipedia days.
Have a good Friday.
Wikipedia articles enlisted in this search for knowledge:
- Plate tectonics
- Pacific Plate
- Hawaii
- Hawaiian Islands
- Hawaii hotspot
- Hawaiian-Emperor seamount chain
- List of volcanoes in the Hawaiian-Emperor seamount chain
- Lōʻihi Seamount
- Hotspot (geology)
- Earthquake
- Volcano
All un-edited images were taken from Wikimedia Commons.
