A geology lesson designed for high school Earth Science students, based on a Duke-UNC Geology Field Trip to the Big Island.

1. Geology of Hawai’i
Lava on the “Big Island”

2. Halema’uma’u Crater at the heart of Kīlauea Caldera
Kīlauea is the youngest of 5 volcanoes
on the Big Island of Hawai’i.

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

4. The process whereby
volcanoes release gasses is
called degassing.
Why do you think
volcanoes undergo
degassing?

5. Hawai’ian eruptions can occur one of two ways:
•Eruption out of a vent
•Eruption out of a rift zone
Spatter cones, like these, form along
rift zones. These spatter cones indicate
Kīlauea’s Southwest Rift Zone.

6. 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 what a rift looks
like along a rift zone.

7. Why is this probably not the best place
to stay on a Hawai’ian vacation?
This is the Volcano House Hotel,
along the rim of Kīlauea Caldera.

8. What can you determine about
This picture shows lava that has
the lava flows, based on what
spilled over the Hilina Pali (a
you see here?
pali is a cliff face).
It is geologists’ job
to come up with an
explanation of rock
formations that
accounts for most of
what they see.

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

10. ‘A’ā is usually several meters high.
‘A’ā!!!
…but it moves very slowly…

11. 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?

12. This is pāhoehoe lava.
Geologists describe pāhoehoe
as smooth and ropey.

13. How do you think the lava
moved to make this structure
form?
Do you see the ropey texture?

14. 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

15. Pāhoehoe lava is often inflated and broken
into structures like this called “tumuli.”
This occurs because of the __________
flowing beneath the cooled lava surface.
FYI: smooth texture ≠ easy hiking

16. ______ 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.

17. 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.

18. 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

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

20. Kīlauea is currently erupting ____ at the surface…
it has been erupting since 1983!
What type of lava is this?

21. Why is the fresh lava mostly
silver instead of red?

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

24. Vanilla Crème Cookie
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.