Saturday, July 23, 2016
Only two mammals were present on the Hawaiian Islands before the arrival of the Polynesians a thousand or more years ago: the Hawaiian Hoary Bat, and the Hawaiian Monk Sea. It's not difficult to understand why: it's hard for any creature that can't fly or swim to get to the islands. Animals have been known to float on mats of vegetation across seas, but it has not happened in Hawai'i. The Polynesians brought animals with them when they colonized the islands, including pigs and rats. Goats, sheep and cows arrived with the Europeans in the early 1800s. They had a devastating effect on the native ecosystems of the islands, but this "cute" squirrel-like animal stands out. It's the Small Asian Mongoose (Herpestes javanicus).
The mongooses run rampant on the Big Island, Mau'i, and Oahu, but were never released on Kaua'i or Lana'i. Efforts are made to trap them, but they are simply too widespread and populous for there to be much hope of containing them. These actions are concentrated on Kaua'i where one was captured in 2012. In their natural habitat in Asia, their predators include snakes, hawks, jackals and storks. Snakes and jackals would be an even worse disaster on the islands (the Brown Tree Snake eliminated nearly all the native birds of Guam). There is a native Hawk on the islands, but there are not nearly enough of them to control the mongooses, and mongooses actually prey on the young hawks at times.
I knew an old lady who swallowed a fly,
I don't know why she followed a fly,
Perhaps she'll die...
I knew an old lady who swallowed a spider,
That wiggled and jiggled and tickled inside her,
She swallowed the spider to catch the fly,
I don't know why she swallowed the fly,
Perhaps she'll die...
In case you don't know the song, we eventually end with a horse, and she's dead of course...
Friday, July 22, 2016
|Lai'e Beach on the island of Oahu, with a coral beach sand stained by iron oxides|
The ocean is relentless. Waves are generated in storms all over the Pacific Ocean basin, and the energy is expended against of the shores of the Hawaiian archipelago. Whatever is there is going to be disintegrated into small particles. Much of the time, two kinds of rock face the waves. Basalt lava flows, and coral reefs. Where does all the color come from?
|Coral sand on the south shore of Kaua'i (can you see any camouflaged creatures?)|
Corals can be colorful when alive, but bereft of living cells, the reef is usually white. The sand that results from waves pounding on the margins of the reefs is therefore usually white as well (Parrotfish also chew up the coral, making sand particles). Basalt is black, but the minerals that make up basalt are high in iron, so when the rocks weather, reddish iron oxides are produced that can stain the fragments of coral to produce reddish or yellowish sands, like those seen above, from the south shore of Kaua'i.
|Kalapana-area lava flow reaching the sea in 2009, from vents seven miles away at Pu'u O'o.|
On the younger coastlines of the Big Island, sand forms in a different way. Lava flows reaching the shoreline can have explosive reactions when encountering the water. The lava shatters into small sand-sized particles, forming black sand beaches. Such beaches will disappear in time, and are thus uncommon. The most accessible beach is Punalu'u on the south side of the Big Island. We paid a visit during our recent exploration.
Punalu'u Beach is a pretty stretch of coast backed by coconut trees, with a seaward projection of lava provides some protection from the worst of the wave action. That makes it a great recreational beach, but also an excellent habitat for Green Sea Turtles (Chelonia myda).
It's a serious thing that turtles and people share a popular beach. It's far to easy to harass and injure the slow moving turtles, and tourists can be real jerks at times. Volunteers are often around to protect the turtles and provide some education. If my pictures seem to have been taken from way too close, remember I have a zoom lens! I can be a jerk at times, but not with these beautiful creatures.
The most unique sand one can find in the Hawaiian Islands is the green kind. These sands are composed of olivine (also known as the gemstone peridot). Olivine is a major constituent of basalt all over the islands, but it weathers rapidly into iron oxide and clay under normal conditions. One can almost always find a few bits of olivine on any gray or black sand beach, but a green beach is a true rarity.
"The Hawai'i That Was" is an ongoing series that is exploring the Hawaiian Islands as they existed in the years prior to the arrival of humans on the island, and the changes that have occurred since then.
Wednesday, July 20, 2016
Tooling around on the southern parts of the Big Island of Hawai'i, one may notice something. Despite the fact that Hilo and the Puna District villages get more rain than any other towns in the United States, there aren't very many rivers. The area is a rainforest, but there are hardly any areas of open water. In fact, a drive around the most of the island, say from Hawi on the north end through Kailua-Kona, around South Point and along the slopes of Mauna Loa and Kilauea, I can't recall seeing a single flow of water. There are a number of reasons. For one, some areas lie in the rain shadow of the big volcanoes. The area north of Kona is practically a desert. On the slopes of Mauna Loa and Kilauea, the reason has to do with the volcanoes themselves.
|Wailuku River from the top of Rainbow Falls|
|Rainbow Falls in Hilo,|
The falls, known in the Hawaiian language as Waianuenue, are steeped in mythology. Stories have grown around the prominent cave behind the falls. It was the abode of Hina, the mother of Maui, the god who created the islands by tricking his brothers into pulling up part of the seafloor, thinking they were hauling in giant fish. A lizard-like monster called Mo`o Kuna kept threatening Hina by sending floods and debris down the river (floods are a common occurrence along the river). Maui came to the aid of his mother, defeating Mo'o Kuna and sending his carcass down the river.
|Pe'epe'e Falls on the Wailuku River upstream of Hilo|
Pe'epe'e Falls are a short distance upstream, and Wai'ale Falls can be seen a bit further up. Wai'ale tends to have the greater volume as water seeps into the ground downstream.
|Wai'ale Falls on the Waikulu River near Hilo|
Hawai'i That Was, is an exploration of the geology and anthropology of the islands, based loosely on our recently completed field course. I expect that the next post will be a bit sandy...and crawling with turtles. Stay tuned!
Tuesday, July 19, 2016
On April 1, 1946, a magnitude 8.6 earthquake struck in the Aleutian Islands of Alaska. The tremor suddenly moved the sea floor, displacing an immeasurable volume of seawater and setting in motion a powerful tsunami. The wave was as high as one hundred feet along the Alaska shoreline, but few people lived there. It was the energy directed into the Pacific Ocean that became the monster that consumed Laupahoehoe. The waves traveled across the ocean at the speed of a jetliner, reaching the Hawaiian Islands just 5 hours later. The waves would have not been noticed in the open ocean because the wave crests were far apart. It wasn't until they reached the shallow sea floor that the full fury of the wave energy would be demonstrated.
|The 1946 tsunami hits Hilo Bay|
|The 1946 tsunami destroys the downtown area of Hilo|
One can only wish that we had had the foresight to set up a similar system in the Indian Ocean prior to 2004. The magnitude 9.2 Indian Ocean earthquake produced a tsunami that killed 230,000 people.
Saturday, July 16, 2016
The pillow basalt is part of the Crescent Formation, a unit that preserves sea-floor sediments and basalt of the ocean crust that was swept into the subduction zone along the west coast of North America. Pillows are globular masses of basalt that form when the lava flows into water. The lava dates from the middle Eocene epoch, about 40 million years ago.
Cape Disappointment is steeped in history, being the last point of solid bedrock along the Columbia River where it flows into the Pacific Ocean. The name came from the failure of early explorers to recognize this spot as the mouth of the Columbia River (hazardous and constantly shifting sand bars made navigation upstream extraordinarily difficult). It was also the place where the Lewis and Clark Expedition finally reached the Pacific Ocean.
There are two lighthouses on the peninsula, due to the aforementioned hazards. Around 200 ships were wrecked in the immediate vicinity over the years.
Wednesday, July 13, 2016
|Mauna Ulu, a mountain that originated between 1969 and 1974|
Hawai'i, especially the Big Island, is different. The entire island is less than a million years old, not even 1/4,000th the age of the planet. Because the island sits atop a hot spot, volcanism is a near constant activity, and volcanism leads to major and rapid changes to the landscape. In this current blog series, we've been talking about the "Hawai'i That Was", the environment that existed prior to the arrival of the Europeans, and before the arrival of the Polynesians. But when we look at volcanic activity at Kilauea on the Big Island, we are looking at landscapes that have never existed before. They are new lands.
My last post on the subject was a discussion of how kipukas preserve a bit of the world that was, prior to the eruption. I said that we visited two of them, but I later remembered that we explored two others as well. It was a trail near Chain of Craters Road that took in two volcanoes, Pu'u Huluhulu, and Mauna Ulu (this is a different Pu'u Huluhulu than the one on Saddle Road).
Pu'u Pua'i in Kilauea Iki, Pu'u O'o, Mauna Ulu (below), and...the dome in the crater of Mt. St. Helens in Washington state! Rapid geologic change is not confined to the Big Island of Hawai'i...
Monday, July 11, 2016
Well, okay, there's not much to be done about it, being that the exposure seen here is on the shoreline of one of the most violent storm-ridden coasts in California, and just a half mile or so from the northernmost land exposure of the San Andreas fault. It's at Shelter Cove on California's Lost Coast, one of the longest undeveloped stretches of coastline in the nation. Except for the small town of Shelter Cove, there is wilderness for a distance of about fifty miles, from Fort Bragg to Ferndale.
The underlying rock is part of the Franciscan Complex, a mixture of graywacke sandstone and shale that was deposited in the trench that once existed off the coast of California in Mesozoic and early Cenozoic time. The gray rocks were uplifted and eroded, and after a stretch of time, were covered by the tan-colored breccia or conglomerate. It was part of the wave-cut cliffs, but was isolated by a fluke of erosion. It's in the active wave zone, so it won't be long before it disappears. The wave-cut bench on which it sits may become a future unconformity if it is ever covered by sediment.