Monday, August 12, 2019

A River Ran Through It

Apologies to Norman Maclean for the play on words in the post title. A venture up the Skagit River valley took me across a swampy forest with occasional stream channels. This venture and a little historic research demonstrates the dynamic nature of the Skagit River.   




These channels will fill with water during flood events on the river. The soils in this area are silts and fine sand suggesting that water flow through this forest, when it does happen, is slow. Hence the channels are slowly becoming filled in by overflow river deposits.

These channels are located in an area where the main channel formerly flowed. The 1881 survey map shows the river formed and island in the river.



An island was still present in 1915.


By 1937 the island was no more but the channel was still evident.


By today the channels are filled in with only a slight appearance in tree type indicating the old channel, but at the far end the old channel remains as a lake as it has not filled as much with sediment.

Friday, August 9, 2019

Slide Complex at Mesa del Oro in the Rio Grande Rift

One of my ventures afforded a view of the Rio Grande Rift in New Mexico.

Rio Grande south of Albuquerque

 J Fleck writes about water in the southwest and the Rio Grande water flows. Viewed from above the contrast of the river and irrigated land is sharp.

Mesa del Oro with large landslide complexes on the west side of the mesa 

Mesa del Oro is a basalt mesa made up of lava flows that have come up along the Rio Grande Rift zone. The mesa also has a thick travertine deposit (Priewisch, Crossey and Karlstrom, 2013). The travertine was deposited from springs with volcanic field associated CO2-rich groundwater.   

Basalt lava flows can break into large landslides due to the weak zones of soil soil between the basalt flows and the vertical fractures that develop in the flows upon cooling. It is hard to have a good sense of scale from 30,000 feet. The mesa is a about 800 feet high. The slide complexes from the top edge of the mesa to outer edge of the slide complexes are nearly 2 miles. I suspect that the slide complex has slowly developed as the top edge of the mesa breaks and collapses onto the slide surface the failed basalt blocks have slid and spread towards the west away from the mesa behaving somewhat like a very slow glacier.      

Thursday, August 8, 2019

The Cascade Range Defeats the Stratus

I have been traveling a fair bit. This has allowed me to have more of an opportunity to enjoy hot weather. Northwest Washington rarely reaches 90. My latest venture to hotter climates afforded a nice view of Mount Saint Helens.

Mount Saint Helens rising above the low stratus
The stratus forms in the cool air coming over the Pacific

On this day the stratus layer evaporates as it crests the Cascade Range
A fairly typical event in Washington summer weather
  

Friday, July 19, 2019

Notes from Castelluccio and Norcia Earthquake Damage

Castelluccio and Norcia are located in the central Apennines Mountain range in Italy. Castelluccio is in a spectacular setting. My first visit here was on a cold spring day that was just above freezing with a chilly fog. Many of the homes in the were abandoned. We were the only guests in the small hotel. A very austere cafe with plastic chairs and folding tables with concrete floor and walls was the only place to eat. However, the cook was incredible and we had an incredibly good dinner and shared our hosts enthusiasm and despair regarding this remote village. 


The town did have a bit of a revival due to tourism associated with outstanding outdoor recreation, spectacular scenery. The cook helped also as he turned out to be a rather talented and famous chef. Italy is a country of great regional pride and people come to Castelluccia for lentils - reportedly at least here as the best in Italy. 

However, an earthquake in 2016 turned much of the town into rubble.     


The hotel we had stayed at was gone. The cafe had not collapsed but was damaged beyond repair. The day we visited there were tourists visiting the flower covered fields or camping on the plain below and going on horse riding ventures into the mountains. Emergency funding had built structures outside of the town so the businesses could continue.     

Damaged building on the mountain pass between Norcia and Cstelluccio with replacement building behind.

Norcia in the valley below was also severely damaged. There is an effort to rebuild some of the buildings including the famous church which for the most part had collapsed. 



We did note some local frustration at the slowness of the rebuilding efforts. Housing erected out side of the city walls has been built, but it is a much different community with so many people no longer living in the city apartments and homes. And tourism has declined with the main Churches destroyed.

The quake was a normal fault slip. The simple story of plate tectonics is that Africa is colliding with Europe; however, some small plate segments are caught between the collision of the two larger plates. The Apulia Plate (or Adriatic) underlies the northeast edge of Italy. 


The collision zone on the southwest side of this plate has formed the Apennines Mountains. The pile up in the collision zone has caused normal slip faulting to develop within the range.



These normal fault segments are not long, but they are generally shallow. Hence, when the slip took place near Norcia and Castelluccio the proximity of the movement combined with gravity wall masonry construction proved to be very damaging.

The recurrence intervals on these types of faults is not well known. In recent years a number of localized very damaging and deadly quakes have struck areas of Italy that had no previous historic damaging seismic events. This has caused a shift in risk approach - but a huge challenge given the centuries of stone construction.

It is clear that Italy has experience shoring up damaged buildings after quakes.





Wednesday, July 17, 2019

Return Home

I have been traveling and busy. Back home with a few observations from the plane trip.

Pools of water on the Greenland ice sheet

Pools of water on and dark ice

Ice flow towards the coast

Note the even longer flow to the sea to the north

Drumlins and river in the far north of Canada

Sand dunes and lakes

Getting close to home - BC Coast Plutonic Complex, the source of many Puget Sound boulders

Coming into Vancouver and the sudden dominance of humans on the landscape
One of numerous massive port facilities 

The delta as the Fraser splits into channels at New Westminster

Miles of log rafts stored along the river banks

Friday, June 21, 2019

Gravel Tongue Draped into The Snake River Canyon

I was going through some pictures of the Snake River canyon through the southeastern Washington Palouse. The four dams on the lower Snake have been the subject of ongoing legal wrangling and policy debate. One big issue that may be under appreciated by some is the transport infrastructure and economy of the dry land wheat on the high plains above the canyon. I have previously touched on the subject of the Snake River and wheat transport (getting-wheat-to-river and mayview-tram-snake-river). There is no getting around the damage these dams as well as the dams in Hells Canyon have done to salmon populations. There is also no getting around how important the dams are for wheat transport. There is no good solution, or if there is, it will be costly. Indeed the existing circumstance has been costly.

The above said, I was looking at a picture of a grain loading facility on the south side of the Snake River just a bit upstream of the confluence with the Palouse River.  

Tongue of gravel descending slope across the Snake River from the grain facility

The facility is located on huge ice age flood bar that formed when the largest flood spilled across the Palouse from Spokane, completely filled the Palouse River valley and spilled out of the Palouse and into the Snake, permanently altering the course of the Palouse River (palouse-falls), and flooded into the Snake River canyon at this location. The flood completely filled the Snake River Canyon and due to the restriction at Wallula Gap water backed up the Snake all the way to Idaho (ice-age-floods-dem-and-lake-lewis).

The tongue of gravel on the slope shown above was from one of the spill over routes of flood water into the Snake River Canyon. It is the easternmost of the spill routes from the ice age flood. The togue of gravel descending down the slope is a rather unique feature. Lidar imagery of the canyon captures this feature rather well.


One more example of the need to reorient one's thinking when in ares impacted by the ice age floods. 

Thursday, June 20, 2019

Summit of Guemes Mountain

Guemes Mountain is on Geumes Island. Guemes is one of the San Juan Islands, but is in Skagit County. It is a very short ferry ride across Guemes Channel from Anacortes on a Skagit County ferry. 

Nothing to do with the mountain but this layer of organic rich muck pulled up by blown over trees along Eden Road was a pretty cool site.   


The trail up the mountain is a moderate climb on a well established trail through a mixed forest stand.


The summit provides nearly 360 degree views:

The view of Anacortes is a reminder that despite the ferry ride and hike, the big city is not far away 

View west along Eden Road with Cypress Island in the distance. 

Cypress is another San Juan Island that is in Skagit County. Most of Cypress is owned by the State of Washington and is managed as a Natural Resource Conservation Area. No ferry service to Cypress.

Jack Island with Lummi Island in the distant right

Jack Island is managed as a natural area by the San Juan Preservation Trust (https://sjpt.org/preserves-easements/jack-island/). It is a rather well hidden island as Guemes blocks the view from Anacortes and the small island blends into the background of other more distant islands when viewed from other angles.

Eliza Island

Eliza is in Whatcom County in the southern part of Bellingham Bay.

Samish Island.

Samish Island is another Skagit County Island. The island is connected to the mainland due to the presence of dikes that hold tidal water out of a quarter mile neck of former tideland. Hence, no ferry is needed to get to Samish. 

The summit of Guemes is underlain by intrusive rocks of the Fildago Ophiolite. The specific rocks of the ophiolite on Guemes Mountain are sheet-like igneous intrusions of granite, diorite, andesite and basalt - likely the roots of an island volcanic arc built up on the underlying ocean crust.
 


Monday, June 17, 2019

Notes From west side of Elwha Delta

I visited the west side of the Elwha River delta. The road dead ends at a trail head at a dike with a wide gravel path along the top of the dike.

Dike trail

Dike trail with estuary pond

View west from the dike

The  dike was built to block the river from cutting hard to the west and eroding the homes and former Elwha village site as well as a cemetery along the shore to the west of the delta. An 1860s map indicates that the village was there at that time. The dike was in place by 1977.  

Oblique aerial view (Ecology, 1977)

The river has since shifted away from the dike so its purpose is not so obvious when walking it today. 

Oblique aerial (Ecology, 2016)

The past few years there has been a very large influx of sediment post dam removal on the Elwha (https://www.usgs.gov/news/moving-mountains-elwha-river-still-changing-five-years-after-world-s-largest-dam-removal). 

One of the gig changes at least in the short term is the expansion of the beach to the west of the delta. The beach has become wider and substantially less steep and has a large accumulation of wood on the uppermost part of the beach. 

beach to the west

Wood on expanded upper beach

outlet of the Elwha

Broad gravel plain along river in the tidal area

I followed a trail through the riparian area of the forest to the river bank and then followed the river to the dike and returned to the trail via the dike trail. Hence, the pictures are in reverse order of my own visit.

Gravel deposits and bars at the former river ford above the delta

sediment and wood deposited within the riparian forest along river

Very high cut bank into the ice age former coastal plain