Hawaii

Hawaii – part III – More Hot Rocks

Until 1969 most of the major volcanic activity on Kilauea was at the summit caldera as described in the previous post. But in that year another centre of activity began at what is now known as Mauna Ulu. This was the start of a trend for volcanism to move to the south East. Currently most activity is at Pu’u ‘O’o.

Activity started along a fissure with lava fountaining out of a mile long crack.

The fissure of the 1969 eruption

The fissure of the 1969 eruption

Most of the lava went downhill as lava flows but there was a spatter upslope which has left a distinctive “Spatter Rampart”.

Detail of Spatter Rampart

Detail of Spatter Rampart

Fissure with associated Spatter Rampart

Fissure with associated Spatter Rampart. The trees are growing in the fissure.

The fissure and associated lava and tephra field

The fissure and associated lava and tephra field

The fountaining lava gave rise to huge deposits of cinders, many of which have a colourful irridesence.

Iridescent lava cinders

Iridescent lava cinders

Also there are abundant streamlined droplets of flying lava called “Pele’s Tears”.

Pele's Tears

Pele's Tears

In a few months the activity had concentrated at the future site of Mauna Ulu and the lava shield began to build. The surrounding countryside was covered with lava and lava flows ran towards the sea. Further along the “Chain of Craters Road” you can see where lava flows from Mauna Ulu ran over a cliff and down towards the sea building lots of new land.

Lava flows came over this cliff to form the land I am standing on

Lava flows came over this cliff to form the land I am standing on

Nearer to Mauna Ulu itself the lava flows covered a tree covered landscape. Often the trees leave a memory of themselves in the shape of “Lava Trees”.

Chris with a lava tree

Chris with a lava tree. Note the mould of a tree on the left. There is another mould above Chris's head.

The lava comes against the tree and solidifies immediately due to the water content of the tree. More lava solidifies and the rest of the molten lava flows past the solid mass. Meanwhile the tree burns away just leaving its shape behind. When the lava stops the level drops and the lava tree is left standing proud.

Mauna Ulu built itself up to a height of 120m above its surroundings. This was done by a series of lava flows like that below.

Chris on a lava flow, Mauna Ulu

Chris on a lava flow, Mauna Ulu

Put a lot of these together and you end up with a lava shield.

The Mauna Ulu lava shield with a perched lava pond

The Mauna Ulu lava shield with a perched lava pond

From the lookout over Mauna Ulu you can see, on a good day, Pu’u ‘O’o where most of todays activity is.

Pu'u 'O'o and Kane nui o Hamo from near Manua Ulu

Pu'u 'O'o and Kane nui o Hamo from near Mauna Ulu. The sharp peak in the distance is part of Pu'u 'O'o. The green hill with fumarolic activity is Kane nui o Hamo. Mauna Ulu is just out of the picture to the right.

There is much, much, more to the geology of Hawaii than I have given here but I hope I have given a taster of what can be seen. I’m disappointed that there was no flowing lava to look at but what I saw was very interesting. I suspect I will have to come back again!

A very good map and pamphlet about the geology of Kilauea can be downloaded from HERE.

Categories: Geology, Hawaii, More Hot Rocks, Places | Leave a comment

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