Posted tagged ‘Coe Glacier’

Parkdale Lava Flow Revealed

April 28, 2012

The new LIDAR data viewer created by Oregon’s Department of Geology and Mineral Industries (DOGAMI) offers a fascinating new look at familiar features in the Mount Hood region. This article focuses on the Parkdale Lava Flow, one of the formations where LIDAR offers an especially striking new look at the geologic story.

Four sections of the Parkdale flow (shown on the index map, below) are the focus of the article.

(for a larger LIDAR view of the entire flow, click here)

The Parkdale lava is of the A’a’ variety (pronounced “ah-ah”), characterized by a thick, pasty molten core carrying hardened chunks of cooled lava on its surface like a crusty skin. This floating skin of jagged, solidified rocks echoes the movement of the underlying flow, thus creating the flow lines. The LIDAR imagery beautifully illustrates these characteristics of an A’a’ flow, including the tall, steep edges of the flow that result from this dense, slow-moving form of lava.

Starting on the north end, at the toe of the Parkdale flow (Map A, below), the LIDAR imagery reveals the flow lines in the once-molten rock in great detail, when compared to traditional maps and air photos. Though the flow was generally heading downhill (the underlying valley floor drops about 250 feet per mile in this area), LIDAR shows it was spreading out, too, as evidenced in the many secondary lobes that formed at the terminus of the flow.

The gentle slope of the open valley floor was responsible for the broad toe of the lava flow, which spread out in the shape of a hand (or paw?) once it emerged from the confining canyon walls of the Middle Fork canyon.

In this lowest extent of the flow, it’s also clear that the lava covered most of the Middle Fork flood plain. Below the flow, the flood area averages about one-third mile in width, but where the channel along the west side of the lava flow, it measures only a out one-tenth of a mile in width.

Moving south to the middle of the Parkdale flow (Map B, below), the LIDAR image shows a powerful, quarter-mile wide stream of lava pushing down a channel at the center of the flow. This main channel also has well defined levees of solidified lava along its margins, a common feature on the more liquid Pahoehoe (pronounced pa-HOI-hoi) form of lava, but less so with the viscous A’a’ lava that makes up the Parkdale formation. More on that point, below.

This view also shows the first lateral lobes, splitting off the main flow as the molten lava reached the open floor of the Upper Hood River Valley, and where the volume of lava overtopped or burst through the levees along the main channel.

The view in Map B, above, also shows how the Parkdale flow pushed the Middle Fork Hood River against the foot of Blue Ridge, to the west. The oversteepened slopes along the west margin of the stream (shown as a distinct shadow) are the result of the Middle Fork continuing to cut away at the base of Blue Ridge, some 7,000 years after the lava flow formed.

Another view of the mid-section of the Parkdale flow (Map C, below) shows fascinating features along the west margin of the formation. Here, a lobe of lava pushed laterally (left) and uphill into the side canyon of Bear Creek, permanently diverting the Middle Fork Hood River in the process.

Molten lava on this scale would have instantly vaporized the Middle Fork as it flowed down valley. But LIDAR shows terraces in stream sediments along Bear Creek near the base of this lobe, suggesting that for some period after the lava cooled, the Middle Fork was backed up, forming a lake. The map below shows what a lake might have looked like, assuming a lava dam formed downstream where the main flow pushed the river high against the slopes of Blue Ridge, creating a 150-foot dam.

The resulting lake might have covered 40 acres and been more than 100 feet deep. The terraces in sediments along Bear Creek suggest the lake existed long enough for a few feet of debris to collect before the Middle Fork cut a path around the lava dam, and allowed Bear Creek to cut through the new layer of sediments.

Did a lava dam create an ancient lake at Bear Creek?

(Click here for a larger map)

The new LIDAR imagery is most interesting at the south end of the Parkdale flow (Map D, below), at the source of the lava. The LIDAR images clearly confirm a single, crescent-shaped volcanic dome that has long been suggested by surveyed contours on USGS topographic maps.

This area is now mostly forested, so the detail provided by LIDAR is the first good look at the radial spread of volcanic material from the vent, initially as more of a mound or cone. As the scale of the eruption grew, a massive stream of molten rock emerged from the north flank of the vent, and began to flow north and downhill, following the broad Middle Fork valley.

The eruption must have been a spectacular event, likely setting off forest fires and impressive steam explosions as the Middle Fork was pushed from its riverbed. It was almost certainly witnessed by Indians living along the Columbia River at the time — perhaps from somewhere in the Hood River Valley, even? It would have been a startling sight, especially at night, and could have lasted from a few days to a few weeks.

The LIDAR images of the vent area also make it easier to imagine the mechanics of the main lava flow. The flow lines on this portion of the flow curve upstream near the vent, as opposed to downstream for most of the flow, a pattern supported by elevation contours: in other words, the upper portion of the flow is concave, or slightly sunken, while the lower flow is convex, or arched upward.

This pattern results from the upper part of the flow deflating as the supply of new lava from the vent subsided, and some of the molten core of the lava flow drained back into the vent, while the rest continued to move downhill under the partially solidified skin. Thus, the upper part of the flow flattened out like a deflated balloon, reversing the flow lines in this section as the skin of solidified lava pulled backward against the hardened levees at the edge of the flow. The effect can be seen in the thickness of the flow: at the toe, the bulging lava flow is upwards of 200 feet thick, whereas the sagging upper portions are less than 100 feet thick near the source.

An analogy for this phenomenon is to half-fill a tube-shaped balloon with water, lay it on a plank, then gradually lift one end of the plank. The effect would be a pooling of water and rounding of the balloon at the low end, and a flattened balloon at the high end. This is how the flow dynamics of the Parkdale Lava Flow unfolded 7,000 years ago.

USGS maps have long suggested a volcanic dome at the head of the Parkdale Lava Flow (marked as point 2825)

As mentioned earlier, the main flow channel of the Parkdale Lava flow has many lateral levees of hardened rock that are more typical of Pahoehoe lava, and yet the rock that makes up the Parkdale flow is clearly of the A’a’ variety. Why was this A’a’ flow comparatively liquid compared to nearby lava flows at Mt. Adams and Indian Heaven, for example?

One reason is suggested in a recent Oregon State University study that shows Mount Hood to have a less explosive personality than most of the other volcano giants of the Cascade Range. Scientists now believe that regular mixing of magma inside the volcano produces a less viscous, less explosive lava than most of Mount Hood’s volcanic neighbors. This research might explain the fluidity of the Parkdale flow, as well.

Fire and Ice?

The new LIDAR images of the Parkdale flow beautifully illustrate how the eruption filled the broad glacial valley of the Middle Fork Hood River from edge-to-edge with lava. Because scientists have dated the flow to about 7,000 years ago, it clearly formed after the end of the Fraser Era glaciation, which ended about 10,000 years ago.

This means the Parkdale flow most likely erupted in the U-shaped valley left behind by the ancestral Coe glacier — a once massive river of ice that included arms reaching into the Eliot Branch, Pinnacle Creek and Clear Branch valleys, as well as the Coe Branch valley, proper. Though intriguing to imagine a volcanic event emerging beneath an ice-age glacier, the glaciers at the time of the Parkdale flow were more like the modern versions we see today on the north face of Mount Hood, high above their ice age extent.

Fire and ice… but not at the same time.

(Click here for larger map)

Though fire and ice did not co-exist here, the path left by ice age glaciers clearly shaped the Parkdale flow. The full extent of the ancestral Coe Glacier is difficult to estimate, partly because the Parkdale Flow has covered the floor of the valley created by the glacier. But the long, straight path of the Parkdale flow clearly follows flat, even terrain that is the hallmark of a glacial valley.

Another possibility is that the formation of the glacial valley, itself, might have triggered a lava eruption after the ice retreated, having carved a low spot where underlying magma could find its way to the surface. That could help explain the flow emerging from this spot on the mountain, far from the active volcanic vents on Mount Hood.

Fire, ice and more than coincidence that a volcanic vent emerged here?

(Click here for larger map)

Equally puzzling in this area is the gap leading to the Evans Creek drainage (marked with “?” on the map, above), which has all the features of a glacial valley, but is separated by a low, 150-foot high saddle from the main Middle Fork valley. Hopefully, the LIDAR imagery will help geoscientists untangle the mystery of these landforms.

LIDAR Art

The striking Parkdale Lava Flow caught the eye of cartographic artist Daniel Coe, and you can pick up his colorized interpretations of LIDAR imagery from the State of Oregon. Coe’s take on Mount Hood and the Parkdale Lava Flow is available in this poster form:

The poster image is also available as a postcard, along with this closer view of the flow:

To purchase these beautiful images, go to the DOGAMI website, and select from the posters and postcards.

To surf the LIDAR imagery yourself, go to the DOGAMI website, and launch the LIDAR Viewer.

Return of the Mountain Goat

March 21, 2011

Rocky Mountain Goats by Albert Bierstadt

Along their return trip across the continent, on April 10, 1806, the Lewis and Clark expedition visited a small Indian village on what is now Bradford Island, in the heart of the Columbia River Gorge. Here, they traded for a beautiful white hide from what we now know as a Rocky Mountain Goat. Meriwether Lewis described it unmistakably in his journal as a “sheep”, white in color with black, pointed horns. The Bradford Island villagers told the expedition the hide had come from goat herds on the high cliffs to the south of what is now Bonneville, on the Oregon side.

Two days later, the expedition encountered another group of Indians, this time near present-day Skamania, on the Washington side of the river. A young Indian woman in the group was dressed in another stunning white hide, and this group also told of “great numbers of these animals” found in “large flocks among the steep rocks” on the Oregon side.

Rocky Mountain Goats by John Woodhouse Audubon

A century later, New York attorney Madison Grant produced the first comprehensive study of the Rocky Mountain Goat for the New York Zoological Society, in 1905. Grant described the historical range of the species extending from British Columbia south along the Cascade Crest to Mount Jefferson. At the time of his research, he reported that mountain goats had “long since vanished from Mt. Hood and from other peaks in the western part of the State, where they once abounded”.

Coincidentally, Grant’s report was published just a few years after the Mazamas mountaineering club formed on the summit of Mount Hood, selecting the Rocky Mountain Goat as their namesake and mascot — apparently, decades after the species had been hunted out in the Mount Hood region.

Early 1900s linen postcard from Glacier National Park

Another century later, on July 27, 2010, the Oregon Department of Fish and Wildlife (ODFW) and Confederated Tribes of Warm Springs made history by releasing 45 Rocky Mountain Goats in the remote backcountry of Whitewater Canyon, on the east slopes of Mount Jefferson, just inside the Warm Springs Reservation.

The Mt. Jefferson release marked a symbolic and spiritual milestone for both conservationists and the Warm Springs Tribe, alike, restoring goats to their native range after nearly two centuries. The release also marked the first step in a major goat reintroduction effort, as envisioned in the landmark 2003 plan developed by ODFW to return goats to their former ranges throughout Oregon.

2010 release near Mt. Jefferson (Photo by Jim Yuskavitch/ODFW)

When the 2003 ODFW plan was developed, about 400 goats were established in the Wallowa and Elkhorn ranges, a few dozen in Hells Canyon, and a few scattered goats had dispersed just beyond these concentrations. The plan calls for moving goats from these established populations to historic ranges in the Oregon Cascades, including in the Columbia River Gorge. The proposed Gorge introduction sites include the rugged Herman Creek headwaters, the open slopes and ridges surrounding Tanner Butte and the sheer gorge face below Nesmith Point. The plan also calls for reintroducing goats at Three Fingered Jack and the Three Sisters in the Central Oregon Cascades.

Members of the Confederated Tribes holding goat kids at 2010 release (Photo by Jim Yuskavitch/ODFW)

The new effort to bring goats back to the Oregon Cascades is not without controversy. Conservation groups have taken the U.S. Forest Service and ODFW to court over lack of adequate environmental review of the plan to bring goats to the Gorge, and the agencies are now completing this work. The legal actions that have slowed the Gorge reintroductions helped move the Warm Springs effort forward, and are likely to move sites near Three Fingered Jack and the Three Sisters ahead of the Gorge, as well.

The 2003 reintroduction plan is also based on selling raffle-based hunting tags that fund the reintroduction program. This strategy is surprising to some, given the small number of animals surviving in Oregon. However, with the raffle for a single tag in 2010 raising nearly $25,000 for the program, it’s clear that selling hunting rights will help guarantee funding the reintroduction effort at a time when state budgets are especially tight.

Mountain Goats on Mount Hood?

The renewed interest in bringing mountain goats back to the Cascades, and the notable omission of Mount Hood from the ODFW plan as a release site, raises an obvious question: why not? The plan doesn’t provide details, but the likely arguments are lack of available habitat and the overwhelming presence of humans on Mount Hood.

The ODFW plan prioritizes sites that can support at least 50 goats, including space for adult males to roam separately from herds of females and juveniles. Without knowing a specific acreage requirement for individual animals, the following comparison of Mount Hood to the Goat Rocks area helps provide perspective — with an estimated 300 mountain goats thriving at Goat Rocks. These images are at identical scale, showing comparative amounts of alpine terrain:

The Goat Rocks (above) clearly has more prime habitat terrain at the margins of timberline, thanks to the maze of ridges that make up the range. But in total alpine area, the Goat Rocks are not much larger than Mount Hood (below), so it appears that Mount Hood has the space and habitat for at least 50 goats.

The human presence at Mount Hood is a more compelling argument against reintroducing goats. The south side of the mountain is busy year-round, thanks to three ski resorts, with lifts reaching high above timberline into what would otherwise be prime goat habitat. Snowshoers and Nordic skiers fill the less developed areas along the loop highway, making the south side one of the busiest winter sports areas in the region.

However, on the east, north and west sides of the mountain, human presence is mostly seasonal, limited to hikers in summer and fall along the Timberline Trail. These faces of the mountain have also been spared from development by the Mount Hood Wilderness, and thus offer long-term protection as relatively undisturbed habitat. This view of the mountain from the north gives a good sense of the many rugged alpine canyons and ridges that are rarely visited, and could offer high-quality goat habitat:

Since we know goats once thrived on Mount Hood, and adequate habitat seems to exist for goats to survive today, the real hurdle might simply be perception — that wildlife managers cannot imagine wild goats coexisting with the human presence that exists on some parts of the mountain. If so, we may miss a valuable opportunity to reintroduce goats where a large number visitors could view and appreciate these animals.

To help remedy this apparent blind spot, the following are a couple of digital renderings of what once was — and perhaps would could be — on Mount Hood. The first view is from Gnarl Ridge, on the east side of the mountain. Here, goats would find plenty of habitat in the high ramparts bordering the Newton Clark Glacier. This area is among the most remote on Mount Hood, so ideal for goats seeking a little privacy from human visitors:

The most obvious Mount Hood habitat is on the north side, on the remote, rocky slopes that border the Eliot, Coe and Ladd glaciers. This part of the mountain is only lightly visited above the Timberline Trail, and rarely visited in winter. It’s easy to picture goats making a home here, on the slopes of Cooper Spur:

(click here for a larger view)

Wildlife managers probably have good reason for skepticism about bringing goats back to Mount Hood. After all, the risks are clearly greater here than at less developed sites.

But let’s reverse these arguments: what if mountain goats were viewed as an end goal in restoring Mount Hood? What if this challenge were reframed as “what would it take for mountain goats to thrive here?” What if successful restoration of Mount Hood’s ecosystems were simply defined by the ability to support an iconic native species like the mountain goat, once again?
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To read an Oregonian article (PDF) on the 2010 Mt. Jefferson goat release, click here.


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