TECH NOTE - Click on the first thumbnail below to begin the slideshow. To proceed to the next image, move the mouse over the picture until the "next" and "previous" buttons appear ON the image or simply use the arrow keys. Enrichment: Virtual Field Trip #1: Hawaii Volcanoes National Park
Hawaii Volcanoes National Park, on the Big Island of Hawaii. Here, we visit the great active caldera of Kilauea volcano. All photos by R., C., J., or K. Alley, except two from the United States Geological Survey (USGS), and so labeled.
Dawn in the 2-mile-wide caldera of Kilauea. Shallow hot rocks produce steam from rainwater percolating through cracks.
Kilauea's "Steaming Bluff" occurs where faults parallel to the 400-foot-high caldera wall intersect the surface, allowing steam to escape. (A caldera, by the way, is a big, complex crater.) (left) In the very-early-morning picture from March 11, 2007, the steam cooled and then was carried down into the caldera by a cool breeze. (right) A little later in the morning, the steam was rising.
Steam rises along faults parallel to but back from the edge of the caldera, which is behind the camera. These faults were caused by the tendency of rocks to slump into the caldera.
Karen Alley films her father in Kilauea’s Southwest Rift. The layered rocks behind Dr. Alley (lava flows, plus pyroclastics--pieces thrown by the volcano) were split in 1971 to form the rift when rising magma inflated the surface like a balloon; an eruption then made the “lava fall” to Dr. Alley’s left.
Above, the Southwest Rift Zone of Kilauea as seen in March, 2007. Right, an aerial photograph, taken in March, 1985, showing the rift. The photo above was taken from the point marked by the tip of the arrow in the right-hand picture, looking in the direction of the arrow. The caldera of Kilauea is behind the camera in the picture above, and at the very top of the picture to the right.
Left, a fern struggles to grow just below the toe of the 1971 lava flow of Kilauea's Southwest Rift Zone. Above, the lush growth near the mouth of the Thurston Lava Tube, on an older lava flow (about 400 years) on the eastern side of the caldera, shows that the lava will yield productive soils if given enough time.
Complex geology. The large rock labeled R above Dr. Alley was thrown by an earlier eruption, and lies in a layer of other pyroclastic pieces. Younger pyroclastic pieces slid off R, so those layers thin as they cross R. The lava flow, the youngest layer, cascaded into the southwest rift to Dr. Alley’s right, ending just above the yellow arrow.
Additional views of features in the previous slide, from the Southwest Rift of Kilauea, labeled in the same way to make them easier to recognize. Later in the semester, you will get a chance to read rocks and tell history CSI Geology. Here, for example, after some lava flows and big explosions, the large rock R was tossed in, then buried by additional things thrown by eruptions, then the rift opened in which Dr. Alley stood to take the pictures, and then a lava flow poured across the top and down into the rift, now ending near the yellow arrow. If CSI Geology does’t make sense yet, don’t worry--it will later.
Volcanic gases include water and other chemicals, from rainwater circulating through rocks, but also from deep in the Earth’s mantle. The atmosphere and oceans formed from volcanic gases. A natural balance has existed for billions of years between the volcanic release of water, carbon dioxide, sulfur (the yellow in the picture above) and other chemicals, and the return of those materials to the deep Earth in subduction zones. Recently, human fossil-fuel burning has been releasing carbon dioxide about 100 times faster than volcanoes do. This is another topic we’ll look into later.
Halema’uma’u Crater, within the larger caldera of Kilauea, is now about one-half mile across and 300 feet deep. From 1905 to 1924, a huge lava lake occupied the crater, often barely 100 feet below the rim (the prominent line marked by the yellow arrow shows where the lava stood at one time). In 1924, the lake largely drained to feed an eruption of the East Rift Zone. Rocks fractured to let the lava out, also letting water in, which flashed to steam and on May 18 caused a very vigorous eruption for “quiet” Hawaii, throwing many-ton rocks as much as 1/2 mile (killing one person). The crater deepened to about 1500 feet, but by 1951 had filled to only half that, and filled further in eruptions of 1974. You don’t need to memorize these details, but we thought you’d find them interesting.
Landslides have fallen down the steep crater walls, often triggered by the shaking of the numerous earthquakes. Notice that muddy water drained out of the big landslide near the center of the photo, forming the light-colored deposit at the point of the red arrow.
Thurston lava tube. About 400 years ago, lava drained through this 10-30 foot high tube. A flow often hardens on the top and sides while remaining molten inside, and the tube drains when the eruption ends. Drips may harden on the ceiling as very strange “stalactites”.
Left: Looking down into a tree mold. When lava hits a tree, water in the trunk boils, removing heat and solidifying a “shell” around the tree. The lava may then drain away, leaving the mold sticking up. In this one, a new tree has rooted in soil developed on the old flow, sending roots into the space left when the old tree burned away. The picture on the right, from the USGS, shows a tree mold a few hours after formation, with the lava still glowing and the tree fallen to the upper right.
Enrichment: Virtual Field Trip #2: Crater Lake Extra
In case you enjoyed seeing Crater Lake, here are even more Crater Lake pictures of posies and geology, including the bizarre fossil fumaroles. If you’ve never seen a fossil fumarole before, click ahead.
Here is Crater Lake in all its glory, as seen from Cloudcap Overlook, with a wide-angle lens.
And here is another look at Wizard Island. This picture was taken on July 12, in 2009, and you can see plenty of snow still present where drifts formed near the lake. The high point on the crater rim at the end of the arrow is Llao Rock, lava that flowed more-or-less along the arrow down a valley from the high peak of Mt. Mazama, before the great eruption removed the high peak.
We didn’t Photoshop the color of the lake. It really is that blue.
The Phantom Ship has a fascinating history. The rocks in this small island are the oldest ones found close to the lake. The Phantom Ship is a remnant of a small volcano that grew before the main bulk of Mt. Mazama, and then was buried by lava flows and pyroclastics as the larger bulk of Mazama grew. Then, when the cataclysmic eruption of Mazama made Crater Lake, the relatively hard rocks of the older volcano were exposed to form the Phantom Ship as the weaker rocks nearby were blasted away. The ridge to the right of the Phantom Ship, just beyond the right-hand tree, is also part of that old, small volcano.
The Pinnacles are fossil steam vents, or fossil fumaroles. During the great eruption, a red-hot “glowing cloud” (nuée ardente) of pyroclastics and poison gas poured down the side of the mountain. When this glowing cloud settled, it made a thick deposit that still extends for miles. Temperatures inside the glowing cloud were probably 750 degrees F or more, so the deposit initially was very hot. The nuée ardente had included steam and other gas. The nuée ardente was deposited on top of more water, that had been in the soil, rocks and plants in the valley before the flow arrived, and that water was turned to steam by the heat. Steam rises, and escaped from the upper part of the new deposit through vents called fumaroles. Minerals carried by the steam, and the heat from the steam, cemented and welded the loose pyroclastic pieces around the fumaroles. Later, after the rocks had cooled, a new stream that formed on top of the deposit cut down through it, washing away loose pyroclastics but leaving the stronger welded parts standing as the Pinnacles. Many of the Pinnacles are hollow; the arrow points to a hole going into this Pinnacle.
Many of the Pinnacles are 100 feet high or more. They are MUCH taller than they are wide. Compare the highest pinnacle in this picture to the tall trees behind it.
The nuée ardente came down the mountain, flowing more-or-less along the red arrow in this picture. Later, Wheeler Creek eroded into the deposit, while flowing more-or-less in the same direction that the nuée ardente flowed, along the arrow (both of them tend to flow downhill). The flat top of the deposit is evident; we added a little yellow line segment along the top of the deposit to guide your eye. Small streams flowing over hard rocks may erode very slowly, changing hardly at all over a human lifetime, but Wheeler Creek carries a lot of snowmelt across loose materials dumped by the volcano, and has cut the deep canyon you see in only a few millennia.
This picture and the next one are not from Crater Lake at all, but from the Valley of 10,000 Smokes. The great blast of Novarupta Volcano in Alaska in 1912 produced a nuée ardente much like the one responsible for the Pinnacles. You can see the steam vents from this Alaskan nuée ardente in the pictures from what is now Katmai National Park. The steam vents have slowly cooled off and no longer are seen in the Valley of 10,000 Smokes. But, someday, erosion there may make features like the Pinnacles of Crater Lake.
The explorers that reached the Valley of 10,000 Smokes soon after the eruption of Novarupta Volcano cooked their dinners in the steam vents.
Meanwhile, back at Crater Lake, this is the “Pumice Desert” just north of Crater Lake. Pumice is the rock version of frozen foam, made when escaping gases blow the lava apart in the eruption. Sometimes, pumice has so much space in it that pieces float in water. The pumice layer is easy to recognize in road cuts, lakes, and other places around Crater Lakes, and can be recognized in Yellowstone Lake, far to the east. (Even floating pumice may become waterlogged and sink sometimes.) The flower in the foreground is a lupine. Lupine often grow in poor soil. The name “lupine” means “like a wolf,” and is based on the old idea that the lupine make the soil poor, “eating it up” the way a wolf would eat a farmer’s sheep. We now know that lupine have the ability to fertilize soil through nitrogen-fixing bacteria that live with the plant’s roots. Lupine move into poor soils where other plants have trouble, and then make those soils better for the other plants. Correlation (lupine grow in poor soil) does not necessarily mean causation (because the lupine do not cause that poor soil).
More pumice, and a pretty yellow composite flower. We’re not positive just which pretty yellow composite this is—the diversity of composites in general, and yellow composites in particular, is legendary—so we will follow standard operating procedure and call it a DYC (darned yellow composite, with the “darned” referring to the difficulty of identification).
The orange Pumice Castle was deposited in a smaller eruption before the big blast, and is now exposed in the cliff on the east side of the lake. Notice the beautiful layering of the stratovolcano, to the left of the Castle.
More layering of the stratovolcano in the cliffs above Crater Lake.
This is a close-up, about a foot across, of a lava flow along the road up to Cloudcap Overlook. The lava is actually obsidian—it cooled before crystals grew, and so is glass. (Pumice and some other volcanic products are also glasses.) This obsidian is not quite the best for making spear points or jewelry, because there is a little too much frothy pumice included (the obsidian is dark, the pumice tan). The frothy part lets you see the small fold in the middle of the picture, made while the lava was flowing.
On the short hike up to Sun Notch, you are walking up an old valley that carried glaciers and streams down from the peak that is gone. This picture looks right up at the was-there/now-gone snow-capped mountain, now replaced by clouds.
The abundant snowfall at Crater Lake melts in the spring to water a lot of wildflowers. Here, the red is indian paintbrush, and you can barely see a purple penstemon behind the paintbrush. This is on the south side of Crater Lake along the Rim Drive, looking south from Dutton Ridge.
These lilies below Sun Notch are variously called glacier lilies, trout lilies, dogtooth violets, and some other names. Whatever the name, they’re still pretty.
Phlox blooms soon after the snowmelt, and prospers on remarkably uninviting-looking “soil.” This phlox is at Merriam Point on the northwest side of the lake.
More paintbrush and penstemon, on the south side of the lake.
An old tree provides an interesting view.
At Vidae Falls, a stream cascades down into the glacially carved valley of Sun Creek.
Like other jays, Clark’s nutcrackers can be rather forward in looking for food from tourists.
The view to the south along the Cascades, from the Rim Drive on Dutton Ridge.
And finally, back to Crater Lake, and Wizard Island.