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Hawaii shelf collapse 12 2005 l.jpg

Hawaii Shelf Collapse 12-2005

The following set of slides is of a recent shelf collapse on the Big Island of Hawaii. During the 2005 Advanced Geology trip to Hawaii, we hiked out to a viewpoint that was close to where this collapse took place. The day we hiked out there, there was a minor collapse that essentially led to this major one. We of course hiked well inland of the coast.

Current lava pictures were taken from http://hvo.wr.usgs.gov/kilauea/update/#video slides 3,4, 19, 22, 27, 32, 33, 34 taken by Dan Brownstein

The images are all from June 29th to Dec 3rd 2005

Slide Show by Daniel Brownstein


Slide2 l.jpg

We were standing several hundred feet upslope of the circle (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30th and we were there on the 29th. Check out the fractures (red and blue ovals) that were right below us in the delta. This is where the collapse took place. Everything to the left of that fracture (the red one) is in the ocean now. The new cliff is 100 ft!


What we saw from that vantage point l.jpg
What we saw from that vantage point (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30


The steam plume on june 29 th visible from over 40 miles away l.jpg
The steam plume on June 29 (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30th—visible from over 40 miles away


We were right here on june 29th l.jpg
We were right here on June 29th! (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30

Our approximate path

July 7

2005

Approx ¼ mile


Slide6 l.jpg

Close up of lava delta July 2005. Note (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30huge crack formed the previous day.

To the left of the crack is “spatter” that came out of the crack when it formed.

Lava is visible entering the ocean at the bottom left


Why shelves collapse l.jpg
Why Shelves Collapse (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30

  • Lava pours into ocean chaotically

  • Layer upon uneven layer leads to a small delta

  • Undercutting by ocean destabilizes delta

  • Eventually the delta will collapse

  • This sometimes forms a series of “steps”

  • A drop down ledge is called a “bench”

  • Next slide diagrams this process


Slide8 l.jpg

1 (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30

2

3

4


Slide9 l.jpg

November 1st (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30

X

We were here

December 1st


Slide10 l.jpg

November 1st (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30

December 1st

45 acres of land

fell into the ocean


Before above after below l.jpg

Point A (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30

Before (above)After (below)

Point B

Point A

Point B


Slide12 l.jpg

Where you shouldn’t stand (see next slide). Note that there are several breakouts just beyond that. This picture is from June 30

Pictures of current flow into ocean over new cliff



Slide18 l.jpg

1. Note location of lava tube (now exposed in cliff face) lava falls

2. Note gypsum/sulfur deposits that formed along new crack near cliff face—these commonly form along fractures above underground lava (see next slide)

Dec 2

2005


Pu u o o current site of eruption along kilauea s east rift zone l.jpg
Pu’u O’o—current site of eruption—along Kilauea’s East Rift Zone

From here—lava travels mainly underground to ocean via lava tubes


Slide21 l.jpg

Lava tubes form because the surface of a lava flow will cool first. Basalt is an excellent insulator and keeps lava underneath new crust relatively hot, which allows it to flow rapidly. When lava cools, it becomes thicker (more viscous) and slows down.


Slide22 l.jpg

Lava tube first. Basalt is an excellent insulator and keeps lava underneath new crust relatively hot, which allows it to flow rapidly. When lava cools, it becomes thicker (more viscous) and slows down.cave—when lava stops flowing it can leave behind a cave like this one. This lava tube is part of a miles long set of tubes on Mauna Loa


Slide25 l.jpg

Current pahoehoe flows. first. Basalt is an excellent insulator and keeps lava underneath new crust relatively hot, which allows it to flow rapidly. When lava cools, it becomes thicker (more viscous) and slows down.Note that within the flow there are black specks. These are solidified pieces of basalt, which slows down the lava


Slide26 l.jpg

Pahoehoe first. Basalt is an excellent insulator and keeps lava underneath new crust relatively hot, which allows it to flow rapidly. When lava cools, it becomes thicker (more viscous) and slows down.


When solidified pahoehoe looks like this l.jpg
When solidified, pahoehoe looks like this: first. Basalt is an excellent insulator and keeps lava underneath new crust relatively hot, which allows it to flow rapidly. When lava cools, it becomes thicker (more viscous) and slows down.


Slide28 l.jpg

Skylight into Lava Tube: Since the top portion of the tube is relatively thin, pieces of the tube can collapse, forming a “skylight.”


Slide29 l.jpg

Skylight into Lava Tube—October 2005 is relatively thin, pieces of the tube can collapse, forming a “skylight.”


Slide30 l.jpg

Psychotic Geologists is relatively thin, pieces of the tube can collapse, forming a “skylight.”


The geologic history of hawaii is filled with examples of much more catastrophic island collapses l.jpg

The geologic history of Hawaii is filled with examples of much more catastrophic island collapses

These collapses can create “mega tsunamis” with waves over 2000 feet tall. Shells carried from such waves have been found thousands of feet above sea level on some of the Hawaiian volcanoes.


Slide32 l.jpg

Note re-growth of delta (only 3 weeks after collapse) much more catastrophic island collapses

Also, the shelf is showing signs of new fracturing


The kohala coast big island l.jpg
The Kohala Coast—Big Island much more catastrophic island collapses


The na pali coast 3500ft kauai l.jpg
The Na’ Pali Coast (3500ft)—Kauai much more catastrophic island collapses


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