Thursday, December 13, 2018

Sauk River Dynamic Channel Migration

The Sauk River is a tributary River to the Skagit. It is in part fed by waters from Glacier Peak and in late summer is cloudy from glacial sediment. After a dry stretch of winter weather, the rive was clear when I recently visited the Sauk a bit up stream from its confluence with the Skagit. 

The Sauk is a dynamic river that moves about on its valley floor. I have made a few geology assessments considering channel migration and subsequent erosion hazards on the Sauk. Others have as well ( My recent trip up the Sauk allowed me to take a look at a river reach I had evaluated 15 years ago.

Well casing has survived the erosion so far

Concrete and piping at former home site

Foundation and septic tank lid

Ongoing bank erosion

For modest homes along the river, stopping channel migration on the Sauk is prohibitively expensive. Besides the permitting issues, the Sauk is a big river with very high flood flows, and thus bank protection would require large scale engineered structural solutions beyond the reach of small rural home owners. Channel movement on some reaches of the Sauk has been as much or more than quarter mile. The lower end right before the confluence is especially dynamic and can readily be seen along the Concrete-Sauk Road.

Lower end of Sauk with broad areas stripped of trees by recent channel movement

That movement has found its way to the valley edge and took a bite out of the Concrete-Sauk Road.

Overflow channel aimed at the Concrete-Sauk Road

Friday, December 7, 2018

Foreset Lava Flow South of Moses Coulee

Much of eastern Washington is underline by the Columbia River Basalt Group. The eruptions took place primarily in northeast Oregon between 17 and 14 million years ago. In central Washington the large lava flows encountered rivers flowing from the north and possible the west. The flows would have dammed the rivers forming lakes. Subsequent lava flows flowed into those lakes. The Columbia River's subsequent carving a deep valley into the basalt flows with some enhancement with the large ice age floods provides exposures to the lava/lake interactions. The interaction of lava flows with water and lake sediments can readily be seen along numerous road cuts and outcrops (columns-and-palagonite) including Interstate 90 west of Vantage. A basalt flow invading lake sediments like an intrusion can be seen at the top of McNeil Canyon north of Chelan (invasive-basalt-at-top-of-mcneil-canyon).   

Along Highway 28 south of Wenatchee there are great exposures of multiple large lava flows. South of Moses Coulee there is a palagonite rich layer that shows foreset bedding structure.        

Angled units within the yellow palagonite and basalt. Younger lava flows on the cliff top did not interact with water and  developed columnar joints upon cooling.

Sunday, December 2, 2018

Lake Crescent and Landlsides

A trip around the Olympic Peninsula typically entails a drive along the shore of Lake Crescent on the northwest of the Peninsula. The lake is one Washington State's largest. By area it is number 6, but by volume it is number 2 behind Lake Chelan.

Lake Crescent 

The lake is within a glacially eroded valley on the northwest flank of the Olympic Mountains. The valley was not carved by ice coming out of the Olympics, but by the massive Juan de Fuca ice lobe that covered much of the area well up the flank of the Olympics.

The depth of the lake has taken awhile to get a handle on because it is so deep. Dartnell, Warrick, and Wegmann (2017) completed a bathnmetry study and came up with a result similar to a depth of a previous effort by Eian Ray and Jeff Enge. These more recent efforts have found a maximum depth of about 600 feet.

The more recent bathymetry shows what appears to be a landslide on the lake floor. The over steep mountain slopes in this glaciated area have failed in the past with several large scale landslides recognized in the area of the lake.

Portion of Schasse (2003) compilation geology map
Blue hatcher line shows estimated elevation of glacial ice
Note several large landslides in yellow

The landslide at the east end of the lake has been interpreted to have dammed the lake, splitting the lake into two lakes, Lake Sutherland and Lake Crescent. This deepened Lake Crescent by about 50 feet and the lake began draining to the northwest via the Lyre River. This new drainage arrangement allowed a new species of fish to develop associated with the lake. 

If one looks carefully while driving Highway 101, the ground between the two lakes is hummocky typical of large landslide deposits. Other slide deposits are evident as well. 

Slide deposit above east shore of lake

The highway crosses a large slide complex to the west of the lake as well.

Lidar bare earth image of slide complex west of Lake Crescent via DNR Lidar Portal

The lake is located in the transition zone between the very wet west side of the Olympic Peninsula a dn the drier north and northeast rain shadow side of the Olympic Mountains.

Lake Crescent and with Storm King Mountain in the distance

Cloud bank on the west ridge of Pyramid Mountain

Tuesday, November 27, 2018

Technical Brush Climbing

Today involved some technical climbing in brush. Our first two attempts to descend a steep bluff were cut off by a vertical drop above the beach. Our third attempt was down through a more recent landslide. The footing was bad due to rooting logs crisscrossed on the ground, the steepness of the slope and slippery soils. The bigger challenge was the thicket of thimble berry with trailing blackberry. 

Geoff working his way back up the slope.
A thick sweat shirt with hood is not a bad gear choice

Geoff making the key crux move

The big plus was the unexpectedly nice weather - sun and 60 degrees in late November was not expected. Much better than the day before with several daily rainfall records broken in the area.

View across Oak Bay to the southern end of Marrowstone Island

Making it to the shore allowed us to assess the lower bluff.

Quimper Sandstone overlain by glacial till
The contact is just above the shovel handle 

Concretions in Quimper Sandstone

Sunday, November 25, 2018

Ice Age Boulders in Drayton Harbor

Drayton Harbor is a shallow bay just south of the Canadian border. The City of Blaine is located on its northeast and southwest sides such that the small city has two parts separated by the bay. 

The predominant geology formation around the bay is glacial marine drift. During the last glacial period, glacial ice in this area was on the order of 6,000 feet thick. That mass of ice load pushed the local land surface downward hundreds of feet. During the late stages of the glacial period, the ice thinned and the area was inundated with sea water with ice floating on the surface. As the floating ice melted, sediment would drop out of the ice and land on the seafloor below. The sediment included boulders. Post ice age the land surface rebounded and lifted the former sea floor above sea level. 

Along the south tidal area of Drayton Harbor, boulders that had been dropped out of that ice sheet are scattered across the otherwise muddy tidal flats.    

Drayton Harbor with three glacial erratic boulders 

The tide was high when I stopped at the shore, so many of the tidal boulders were covered. Just about every time I pass by this shore, a great blue heron is using one of the rocks as a resting perch.

Friday, November 23, 2018

Eastern Washington Ice Fog and Riparian Forest on the Columbia

Much of eastern Washington is dry. Total precipitation is as low as 6 to 7 inches in the driest parts. However, winter is not necessarily sunny in these dry areas. The bowl-like shape of the Columbia Basin traps cold air that tends to stagnate as a blanket of chilly fog. The result can be days no sun.

Over the past week the fog was spotty as I meandered about on my various ventures. The temperatures were cold enough to brighten the landscape with the fog freezing on the plants.

No distant views on this stretch of the trip

Flocked trees at Verneta

The Columbia River is warm compared to the air and adds to the fog near Priest Rapids

The fog thinned near Mattawa and the orchard/vineyard windbreak trees provided a nice winter show 

The fog was limited to the lower Columbia Basin on this day and I broke free of the fog at Sentinel Gap 

Much warmer and bright north of the gap at a familiar line of trees along the river downstream of the old rail bridge. I wrote a report on this tree stand a while back. The evergreens are junipers. They as well as the other river front trees have become progressively thicker since. The tree stand is not "natural", but is the result of alteration of the flow regime on the river. The big yearly floods of the past are no more and hence the riparian areas are not as dynamic as there were in the past allowing trees to become established along the river side. The development of these riparian forest zones has created new ecosystems along the Columbia River.

Thursday, November 22, 2018

Silica Road

Interstate 90 crosses the Columbia River at Vantage. Heading east the highway climbs up out of the deep river valley to the tops of the basalt cliffs and skirts the northwest end of the Frenchman Hills and enters the Quincy Basin.

Silica Road is a familiar exit for Gorge concert goers. The concert venue is located at an ice age spill way where flood water from ice age floods spilled out of the Quincy Basin into the Columbia River gorge. 

Silica road passes through an area of surface mining. The mines mine silica from old lake beds that formed between lava flows of the Columbia River Basalts.

White area on horizon is one of the mines

The silica is diatomaceous material. That is the silica is the accumulation of diatom shells on the lake beds. The lakes must have received very little sediment and thus the diatoms were the primary sediment accumulation in the lake bed. Diatomaceous material has lots of uses from high quality water filters to natural pesticides (the rough mirco glass structure of the silica is hard on bugs).

The ongoing mine activity is located both south and north of the Interstate.

Mines north of Interstate 90. Silica Road passes through this area on the way to the Gorge.

Mines south of Interstate 90.

The mine reclamation requirements are overseen by the Washington State Department of Natural Resources. The mines to the south of the Interstate are in areas with preexisting soil cover and have been reclaimed back to agricultural use. I recall one mine received an award for the reclamation work completed.