for Miss Jordan's Class
Hi everyone! I was fascinated by one of your class blog posts because it showed you had been learning about one of my favourite topics, Volcanoes in Science.
I thought I would send a few small samples from my visits to volcanoes in New Zealand and Hawaii some time ago. I'll also share some new video clips from my video library.
Your samples sent are...
Many of the world's volcanoes formed along tectonic plate borders. These "plates" are large areas of our world's solid surface floating on the molten magma layers below. It's a little like ships floating on the sea.
You can see Australia lies on its own plate but New Zealand is on the border between the Pacific and Australian plates.
New Zealand and its volcanoes are formed over the the tectonic plate border but can you see Hawaii? Its a small mark on the map in the upper middle of the Pacific Plate (yellow).
Hawaii formed over what is known as a hot spot. On these spots, it's thought the magma underneath the plate is particularly hot. As the Pacific Plate moves very slowly over the hot spot, new volcanoes start to build. Old ones erode back into the sea.
Below is an image from Google Earth. You can see the Hawaiian Islands near the bottom. Can you see the line of old volcanoes now below the ocean moving up to the left?
Hawaii is a collection of old and newer volcanoes. There is thought to be a much newer one forming below the ocean about 30 kilometres off the Big Island of Hawaii in an area known as the Lö'ihi Seamount. Don't expect it to be above the ocean surface anytime soon. While it rises about 3000 metres above the ocean floor, it still has over 900 metres to go before it reaches the surface. Aren't volcanoes interesting?
Let's Look at your samples...
While there in 1996, I learned Hawaiians talk of two types of lava. They are Aa and Pahoehoe.
Aa (ʻAʻā) - These stones are hard and have sharp edges. Your samples are only small but they can be much larger. I don't know why but perhaps Hawaiians named it this because of the sound you make when you try to walk on it in bare feet when it has cooled.
This basalt lava is cooler as it flows and is rubbly on its surface and edges.
Pahoehoe - Is a smoother basaltic lava that flows more like cool honey does when it flows. Your sample was from an active flow of lava I saw on my visit. It tends to break down into a black sand when crushed or stepped on.
In my video library, I have a video clip to show a pahoehoe flow. My cameras weren't up to it back then so I had to buy this clip. It has been speeded up because its flow can be quite slow.
This clip is not to be copied or linked in any form. It was a royalty-free purchase through Videoblocks.com.