Geology of Hawai'i - Lava

Geology of Hawai’iLava on the “Big Island”

Halema’uma’u Crater at the heart of Kīlauea Caldera

Kīlauea is the youngest of 5 volcanoes on the Big Island of Hawai’i.

This vent within Halema’uma’u is emitting toxic sulfur dioxide gas. In total, the volcano emits about 1000 tons of sulfur dioxide each day!

Smog that results from all the gas being emitted by the volcano is called vog.

The process whereby volcanoes release gasses is called degassing.

Why do you think volcanoes undergo degassing?

Hawai’ian eruptions can occur one of two ways:1.Eruption out of a vent2.Eruption out of a rift zone

Spatter cones, like these, form along rift zones. These spatter cones indicate Kīlauea’s Southwest Rift Zone.

This is what a rift looks like along a rift zone.

This is called a spatter rampart.It forms when lava spatters into a mound beside a rift (like the one below).

How do you think a spatter cone would form?

This is the Volcano House Hotel, along the rim of Kīlauea Caldera.

Why is this probably not the best place to stay on a Hawai’ian vacation?

This picture shows lava that has spilled over the Hilina Pali (a pali is a cliff face).

What can you determine about the lava flows, based on what you see here?

It is geologists’ job to come up with an explanation of rock

formations that accounts for most of what they see.

This is ‘a’ā lava.

Geologists describe ‘a’ā as “clinkery” because its surface is broken and rocky.

‘A’ā!!!‘A’ā is usually several meters high.

…but it moves very slowly…

Sometimes ‘a’ā can hold treasures called xenoliths! Xenoliths are awesome because

they are pieces of the Earth’s mantle…a layer humans have never been able to reach!

What can xenoliths tell us about the mantle?

This is pāhoehoe lava.

Geologists describe pāhoehoe as smooth and ropey.

Do you see the ropey texture?

How do you think the lava moved to make this structure form?

Our first sighting of magma!As you can see, it was flowing beneath the surface.

Magma = molten rock beneath the Earth’s surface

Lava = molten rock on the Earth’s surface

FYI: smooth texture ≠ easy hiking

Pāhoehoe lava is often inflated and broken into structures like this called “tumuli.”

This occurs because of the __________ flowing beneath the cooled lava surface.

______ can flow for great distances underground in cave-like structures called lava tubes.

Being underground keeps the magma hot, and allows it to keep flowing.

Lava tubes allow magma to flow all the way to the sea from the eruption site, which is usually several hundred, or even a few thousand feet away.

Black sand beaches form when regular hot lava enters the sea and cools so rapidly that it shatters into tiny sand grains.

Olive Ridley Sea Turtle

Green sand beaches form when hot lava with lots of the green mineral olivine cools rapidly in water and shatters into sand.

Kīlauea is currently erupting ____ at the surface…it has been erupting since 1983!

What type of lava is this?

Why is the fresh lava mostly silver instead of red?

Fresh pāhoehoe has a temperature of 700-1200 °C…that’s 1300-2200 °F!

It is said, one must submit an offering to Pele, the Hawai’ian goddess of the volcanoes, in exchange for the privilege of visiting the volcano.

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