# Po'ipu Geology



## T_R_Oglodyte (Sep 13, 2007)

Regulars here know I'm a bit of a geology buff. If that kind of thing doesn't interest you, move on now. 

I put up these two photos in a different thread, showing some of the area around the Sunterra Poi'pu resort. The photos look east along the Koloa area shoreline toward Ha'upu, the tall mountain on the left side of the photo. (Ha'upu is also the mountain used in the opening shots of the first Indiana Jones movie, but that shot is from the other side of Ha'upu.

*Poipu Point resort, Shipwreck Bay, and Makewehi Cliffs*






*Rain clouds over Ha'upu*





The top photo is taken just south  of the Sunterra Po'ipu resort, looking northeasterly across Shipwreck Bay.  The white cliff on the far corner of Shipwreck Bay is the start of the Makewehi shoreline cliffs.  The second photo was taken along the Makewehi shoreline, beyond the cliff shown in the first.  This photo looks across the next bay to the east of Shipwreck Bay.  Note the very light colored area on the far shore (that I caught just as it was illuminated by a patch of sunlight) and how those rocks are dissimilar from the darker brown rocks surrounding it on the top and both sides.

****

Now a bit of context.  Hawai'ian volcanoes go through a specific death sequence.  As the island moves away from the hot spot firing the volcano, the volcano stops erupting and is dormant for hundreds of thousands of years.  Finally, as it's last action, the volcano rejuvenates in a series of final eruptions that create various smaller cones and creating a series of lava flows.  Diamond Head on O'ahu is a prominent later phase eruptive cone. On Kaua'i Kilohana is a late phase cone, as are all of the cinder cones and small craters in the Po'ipu area.

On Kauai'i those late phase lava flows are called the Koloa formation and they are easy to identify because of their characteristic brown color.  The Koloa flows are responsible for all of the level benchlands around the island.  For example, on the drive from Kapa'a to Hanalei, as you climb the hill ust past Kealia Beach (and the road swings inland a bit away from the coast), you are climbing onto a Koloa lava flow.  You stay on that flow all the way through Princeville. The descent to Hanalei Valley just past Princeville is where you leave the Koloa benchland. From Hanalei to Ke'e Beach, everything you see is old island.

*****

Returning now to the pictures.  First note that the Makewehi Cliffs are not volcanic at all - they are entirely lithified sandstone.  In the second photo you can see the striations clearly. Also in the second photo you can see how the Makewehi Cliffs are older than the Koloa flows - on the far side of the bay the Koloa flows completely covered the Makewehi sandstones.

For the second part of the story, consider that in the second photo the Makewehi Cliff you see across the bay at some time must have been continuous with the cliffs where the photo was taken.  Returning to the first photo, if you are at the Suterra resort and look around the waterfront area on near the north side of the Sunterra property (near the public parking area next to Building 9), you will find the sandstones, again with some Koloa lava overrunning the sandstone.  From that point you can look across Shipwreck Bay to the Makewehi Cliff and see how those two points were once connected as well.

Assembling the pieces, at the end of the Koloa eruptions the shoreline in this area was further out from where it is now, and consisted of Makewehi sandstones, overrun in areas by Koloa flows.  Shipwreck Bay in the top photo and the smaller bay in the second photo did not exist, because the line of Makewehi dunes marked the shoreline.  Wave action subsequently breached the dunes and exposed the area landward of the Makewehi sandstones.  Being softer than the Koloa lava, when the dunes were breached, the waves could readily undercut the Koloa lava and widen the Bay opening.  

The Makewehi cliffs have survived direct exposure to the waves only in the areas where they stood taller and were thicker, such as where I was when I took the second photo. But they are eroding and will soon (in geologic time) be gone.

This same pattern is repeated over and over along the entire coastline from the Sunterra Resort to the point where the Ha'upu ridge line reaches the ocean. 

From the Brennecke's Beach area westward to beyond Spouting Horn, all the exposed rocks on the shoreline are Koloa lavas.  If there are any dune rocks in that area, they were completely covered by the Koloa flows.

******

Final note - many of the waterfalls on Kauai'i are created when rivers reach the end of a Koloa flow.  Because the Koloa flows resistant erosion better than the underlying, older rocks the river water undercuts the Koloa flow, creating a cliff for the water to flow over.


----------



## Fisch (Sep 13, 2007)

*Ha'upu another shot*

http://www.flickr.com/photos/fischproductions/1365460882/

Couldn't get the picture to embed.  I'll figure this out sometime


----------



## Henry M. (Sep 13, 2007)

So do you think Haleakala in Maui will come back for one final farewell or is it just falling deeper into sleep and may actually be close to extinct by now?


----------



## Tiger (Sep 13, 2007)

Beautiful shots Steve.  The hikes along those cliffs are some of the very best on Kauai.  The horse tour is also a lot of fun.


----------



## T_R_Oglodyte (Sep 13, 2007)

emuyshondt said:


> So do you think Haleakala in Maui will come back for one final farewell or is it just falling deeper into sleep and may actually be close to extinct by now?



Haleakala will almost certainly come back for it's final farewell.  It has had few, if any, late phase eruptions.  West Maui is done.


----------



## T_R_Oglodyte (Sep 13, 2007)

Tiger said:


> Beautiful shots Steve.  The hikes along those cliffs are some of the very best on Kauai.  The horse tour is also a lot of fun.



I really like the Makewehi Cliffs to. I explored them for the first time about four years ago, and now they are one of my favorite areas on the island.

Here's a closer up photo showing clearly how the Koloa flow buried the Makewehi sandstone.


----------



## Tiger (Sep 13, 2007)

I don't know when was the last time you were there but within the last 18 months or so there was a major landfall into the sea right in the middle of your last shot.  The trail is now routed onto the grass of the golf course in that area and it is roped off.


----------



## T_R_Oglodyte (Sep 13, 2007)

Tiger said:


> I don't know when was the last time you were there but within the last 18 months or so there was a major landfall into the sea right in the middle of your last shot.  The trail is now routed onto the grass of the golf course in that area and it is roped off.



That photo was taken about four weeks ago.


----------



## Kauai Kid (Sep 13, 2007)

Aloha:  When will your first Kauai book be published?  Hope it is an underground press so the Maui folks don't learn about Kauai.  Underground also for the geology lessons.   

Sterling, Poipu Point Oct 6-20


----------



## T_R_Oglodyte (Sep 14, 2007)

Kauai Kid said:


> Aloha:  When will your first Kauai book be published?  Hope it is an underground press so the Maui folks don't learn about Kauai.  Underground also for the geology lessons.
> 
> Sterling, Poipu Point Oct 6-20



The terrain has already been covered, so tto speak. If you are interested in island geology, _Roadside Geology of Hawai'i_ is as essential as Andrew and Harriett's _Revealed_ guidebooks.

FYI - after we returned from our trip to Hawai'i last month, I forwarded to Dr. Hazlett, lead author of the _Roadside Geology of Hawai'i_, my photo of the Kilauea lava filed showing the slumpage cracks that are less than 25 years old  (Click here.)  He was very interested and is apparently considering including the photo in a future edition of _Roadside Geology of Hawai'i_.


----------



## nicklinneh (Sep 14, 2007)

steve-
what an informative narrative on the K geology, detailing your great pictures. I hope you'll submit more like this. I'm sad I didn't know about the Roadside book when we went to BI in June. ---ken


----------



## T_R_Oglodyte (Sep 14, 2007)

With thanks to Greg G, who posted a Picasa photo album that has exactly the pic I was missing of the connection of the Makewehi Cliffs across Shipwreck Beach.

The pic below is from Greg's Picasa photo album, taken at "Hyatt end" of the Po'ipu Point resort grounds - i.e., the other side of the resort from where I took the picture I posted above.






The rocks in the foreground of Greg's picture are  Makewehi sandstones that originally were part of the same sand dune formation that formed the cliff on the other side of Shipwreck Beach that appears just on the right edge of Greg's picture. 

Shipwreck Beach was formed when the ocean breached the cliffs.  The ocean likely broke through here because this was a low spot in the dunes, as indicted the by the difference in elevation between the spot where Greg took the picture and the top of the cliff on the other side of the Bay.  Also, the Koloa lava flows behind the dunes (i.e., in front of the Hyatt) don't appear to have been as thick as they are at the Sunterra Poi'pu Point resort.  That also would have made it easier for the waves to cut a new bay where Shipwreck Beach is now. In contrast the lava between Brennecke's Beach and the Hyatt resort was thicker and resisted erosion, so that area now juts in the water as a point of land (and creating the wonderful views, with the crashing waves, and great turtle habitat).


----------



## dmharris (Nov 1, 2007)

Steve,

Thanks for this great lesson.  We were over at the Po'ipu resort for a timeshare tour and were wowed by this beach, the view, the turtles, etc.  Great to have the geological history behind it.


----------

