Tuesday, May 24, 2016

Lime Kiln on Orcas

An early resource extraction in Washington State was limestone. Limestone deposits were mined on Orcas Island and San Juan Island. The mines and associated kilns on San Juan Island are a bit better known as State Park, Lime Kiln State Park is located at the site. Kilns and small mines were also located at the upper end of East Sound southwest of what is now the Town of Eastsound (the town name runs the two words together). I came across one of the old kilns covered with English ivy.  

I know of at least two other kiln sites on Orcas. Another kiln site is located on San Juan Land Bank property at Judd Cove (sjclandbank.org/judd-cove-preserve-orcas-island) and is open to public access.

USGS topographic map indicating two kiln sites
The kiln shown above is not on the map

The limestone is in or were in three different formations: the Eastsound Group, the Deadman Bay Volcanics and the Orcas Chert. In all three cases the deposits are small in extent. However, the high carbonate content, access to water transport and abundant fuel (forests) for firing the kilns allowed for these small deposits to be profitable. There are scattered old quarry sites at many sites near the water on the island. The mining took place as early as the 1860s and was still in operation into the 1910s.

Monday, May 23, 2016

Two Different Erratics on Samish Island

I have found that my visual memory from past field work has lingered. I readily observe and notice certain rock features from past field work habits. While walking a gravel/cobble beach on Samish Island in Skagit County, I spotted small boulder among the thousands of other rocks on the beach.

Garnet and kyanite/sillimanite (and maybe andalusite psuedomorphs) schist

I spent a fair bit of time during a past geology work era looking for aluminum silicate schist. The whitish minerals in the rock are likely mostly kyanite with some sillimanite. And as noted might have once had andalusite that was replaced by the kyanite. These three minerals form under different pressure and temperature regimes with anadlusite being the lower temperature and pressure member, kyanite the high pressure member and sillimanite the high temperature member.

Identifying any of the three can give one a rough idea as to the pressure and temperature of the metamorphosed rock. And if you can identify the shape of one mineral such as the small crosses andalusite forms being replaced by say kyanite you can get an idea of the pressure/temperature path of metamorphism. Having the garnets in the mix can further help determine the pressure temperature path as the composition of the garnet shifts based on pressure and temperature as well. The core, central part of the garnet, will have a different composition than the rim. Hunting for this type of rock in the Coast Range of British Columbia or the crystalline core of the North Cascades took up a fair bit of my field time while working in those areas.

The boulder on the beach that I readily spotted would have been delivered via glacial ice from the high ranges of the BC Coast Range and may be from the same schist unit I once collected samples from.

I also spotted a much smaller erratic on Samish Island:
Dunite pebble

This pebble of dunite was not delivered by glacial ice. It had arrived via truck and was part of the gravel road I was walking. A pebble of dunite would not be a surprise given that many of the Skagit County gravel pits extract gravel deposited from an ice age river system that had some source material that came off of the Twin Sisters Range, a block of dunite within the Northwest Cascades. 

Saturday, May 21, 2016

Damming the Columbia: The Bonneville Landslide

I was curious about what the backup of the Columbia River would have looked like when the Bonneville Landslide at Bridge of the Gods blocked the Columbia River. In the DEM (digital elevation model) I set the blue color at 80 meters corresponding with the approximate top of the landslide deposit. The result is a long lake that extended well beyond the Columbia River Gorge and backed water up to approximately present day Umatilla, Oregon.

This assumes that the dam held up until it was nearly over topped. Lewis and Clark recognized the landslide when they traveled down the river having observed stumps from a previously drowned forest. They suggested the slide was 20 years old. The forest stumps were a well known feature of the lower Columbia River Gorge prior to the redrowning of the stumps when Bonneville Dam was built.

Pat Pringle gives a good overview of the slide complex with a discussion on the dates of the slide (bonneville_landslide_explorations.pdf). The slide is more likely about 550 years old based on carbon dates and tree rings.

(Randall, 2012) provides a more detailed characterization of the landslide complexes in this area. 

Wednesday, May 18, 2016

Fishhook Jim and Fishhook Park

Fishhook Park is Army Corp of Engineer Park on the shores of impounded Snake River above Ice Harbor Dam. The park has camp sites, picnic areas, swimming areas and boating facilities associated with recreating on the lower Snake River. During a past era, I spent a fair bit on the lower Snake. In the summer the water is a lot warmer than the frigid Columbia.

The name Fishhook is derived from a rapids that was formerly located on this reach of the Snake River. But it also derived from a former resident, Fishhook Jim. I suspect his name was derived from the place.

Fishhook Jim was a Palouse Indian. The Palouse had releations and intermingled with many of the other tribes of the inland Pacific Northwest. The Palouse did not have a designated reservation in the Walla Walla Treaty of 1855. While some Palouse went to live on the Yakima, Nez Perce and Colville Reservations, many Palouse simply stayed put and continued to live along the Snake River with seasonal trips to other food source sites. Fishhook Jim was the descendent of Palouse Induians that stayed. Eventually nearly all the Palouse were forced to leave. A few managed to obtain homestead claims - a hard task for Indians that took the American path of land ownership. Frequently Indians were not allowed to claim land even if they opted not to go to the reservation. But for the few that did manage to stay, another blow came with the building of the dams on the lower Snake. The rapids at Fish Hook disappeared under the water as well as the ancestral village and gathering sites. It should be further added that several salmon species on the lower Snake were also finished off by the dams.

Fishhook Park is a reminder of a past time and a gesture by the dam builders to remember what was once there as well as the people that once lived for thousands of years on the lower Snake.

William Clark described the Corps of Discovery trip through Fish Hook Rapids:

"... A cool morning, deturmined to run the rapids ... [Clark, October 16, 1805]
Having examined the rapids], which we found more difficult than the report of the Indians had induced us to believe, we set out early, and putting our Indian guide in front, our smallest canoe next, and the rest in succession, began the descent: the passage proved to be very disagreeable; as there is a continuation of shoals extending from bank to bank for the distance of three miles, during which the channel is narrow and crooked, and obstructed by large rocks in every direction, so as to require great dexterity to avoid being dashed on them. We got through the rapids with no injury to any of the boats except the hindmost, which ran on a rock; but by the assistance of the other boats, and of the Indians who were very alert, she escaped, though the baggage she contained was wet.

Saturday, May 14, 2016

Non Washington: Aerial Notes from Nevada

Flying into Las Vegas, Nevada is a always a great treat for a geologist with a window seat or for anyone that appreciates landscapes.

A top highlight is the classic Keystone Thrust:

The older rocks of the layered limestone rocks of the gray Cambrian-age Bonanza Formation are overlying the buff to red sandstone of the younger Jurassic-age Aztec Formation. The older rocks were thrust up and over the younger rocks approximately 70 million years ago with an estimated crustal shortening of 60 miles. There are plenty of thrust faults in Washington State, but not nearly so well exposed and easily seen.

To the west of the thrust fault, the older rocks are also folded. Again demonstrating the crustal shortening or compression that took place in this area.

Geologic hazards are also readily observed, such as flood hazards. Nevada is full of alluvial fan areas with associated flood, erosion and sediment deposition hazards.

Dam and excavation on right to capture and hold water and sediment to protect Las Vegas development on the left.

Parhump has seen rapid residential development with very little regard to flood hazards associated with alluvial fans. The approach to development appears to have been build first and then solve the flood hazards after floods take place. Parhump experienced flooding in 1997 and twice in 2003 including flood waters as deep as 3 to 4 feet (Nevada Division of Water Resources, 2013).

Efforts to assess the hazards have included detailed mapping of piedmont and playa features (House, Buck and Ramelli, 2010). The broad fan below shows a variety of ages on its surface and illustrates the fact that alluvial fans are complicated and subject to change during flood or debris flood events.

The Las Vegas River has caused flooding and erosion in Las Vegas that has led to a variety of flood projects on the river. But given the drought risk that Las Vegas lives with, water in the river is a good thing. That water is actually waste water from the waste water treatment plant. The water is simply being returned to where it was drawn from.

Flowing water in the Las Vegas River

The long drought is evident when Lake Mead came into view.

Bath tub ring around Lake Mead on the Colorado River

Nevada is well know for mining. Part of the fun of flying over the state is mine spotting. Below is a the classic gold mine operation with heap leaching to extract the gold from the ore:

See SF's post for some geology and other references for this area

Nevada has non metal mines as well including mountain top mining for limestone and mountain top development.

Limestone mine outside of Las Vegas for cement production

Building pads for home development in south Las Vegas 

The biggest recent alteration of the landscape of Nevada the past few years has been huge solar farms:

Distant view of solar farm 

Friday, May 13, 2016

100 Years of Good Work

Capitol Reef Visitor Center

This year marks the 100th anniversary of the National Park Service. America's National Parks are something to be proud of, and we should be proud of the great park service that has served our parks and us so well. I paid a recent visit to a few of the parks in southern Utah. While I often seek out more remote places, I really enjoyed sharing some more visited sites with others.

Delicate Arch is not a place to go for solitude. I did have the site to myself the first time I visited it. A heavy snow storm brought about that lonely venture. The arch is a remarkable feature, and this time I very much enjoyed sharing the site with other hikers. One of the many great places to enjoy as a nation.

Saturday, May 7, 2016

Boulder Lag Beach

This shoreline stretch on the Salish Sea is nearly all boulders. Most of the boulders matched the local bedrock geology, but there are plenty of exotic boulders from far away places brought by the ice age glacier.
The source of the boulders is a glacial drift deposit along bluff above the beach.

Glacial drift with some stratification

Glacial drift directly deposited on bedrock

The shore has enough wave energy to removed the silt, sand and gravel from the beach leaving behind a lag of boulders. The headlands at bot ends of the beach were bedrock points. Any sand and small gravel had been transported into deep water off the points and outward from the boulder lag beach.