1/ Spent an enjoyable Friday (March 15) with the amazing Dr. Corinne Griffin on the EASC 403 Quaternary Geology Sea to Sky Fieldtrip. It covers glacial geology and, naturally, Natural Hazards. #SFUNaturalHazards#SFUGlacialGeology
2/ Charles Creek Debris flow retention structure. Poor land use decisions (not recognizing debris flow hazard on fan deltas) resulted in deadly consequences followed by construction of several types of debris flow protection structures. They work.
3/ Porteau Cove. Area of shallow water because of a submarine moraine, makes this a good site for a ferry dock and diving. Day lighting joints along road can lead to rock fall issues, such as happened in July 2008. Caused a bit of a kerfuffle in terms of the Olympics.
4/ Britannia beach delta. Most of gravel now gone but still some bottom sets, includes molds of shell confirming marine conditions.
5/ Mamquam Delta. Great example of a gilbert style delta that resulted from a younger dryas readvance of glaciers down the Squamish Valley, forming a lake in the Mamquam, that then overtopped the site.
6/ Checkay fan/dike. Development on the Chekeye Fan is constrained by the potential of Debris flow hazard and flooding hazard. This dike is in repose to the flooding hazard. Floodwater have come close to overtopping this dike.
7/ Streamlined bedrock. Located right across from Stawamis Chief this outcrop shows evidence of both basal glacial erosion and meltwater erosion. Great discussions.
9/ This weekend the group is in the scablands! Wish I was there!
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On August 29 examined some active layer detachment slides Near Arch and Quill creeks, SW Yukon. Around 25-30 slides occured on August 17, the same time the Alaska Highway was blocked by debris flows. A thread of these. This is the slides near where we landed. 1/10
Landed on the deposition zone of one of the landslides and flew the drone. Helicopter indicated for scale. 2/10
This is part of Crey Ackerson’s MSc thesis supported by Kristy Kennedy from the Yukon Geological Survey. 3/10
Finally some pictures of the Koidern Landslide. Start with some aerial pictures and then some more details. Some really interesting mollards, and some have remobilized! It is a long thread as it was a really cool landslide! 1/10
Looks like several phases. Initial failure crossed the small valley and then turned the corner. Then remobilization with a more fluid flow down the valley, blocking the larger stream. Then a smaller failure from the headscarp, where we first landed the helicopter. 2/10
Margin of the slide with lots of mollards. Nice streaking of the bedrock. 3/10
Spent a beautiful Friday at Point Grey (aka Wreck Beach) looking at the stratigraphy. He we have two advance sub-units below the till. The lower is interstratified sand and silt with peats, with ages from 26-24 ka, the upper, cross stratified sand. 1/
These advance sediments are called Quadra Sands and some diatoms in the lower sub-unit sediments indicate marine incursion. The upper sands show tidal influence. With eustatic sea level at this time, indicates >100 m of isostatic depression! 2/
The accumulation of ~70 m of Quadra sands indicates significant accommodation space. The two sub-units are exposed all along the escarpment. 3/
Friday’s Seymour valley fieldtrip examined the stratigraphy of the thick valley fill. The base is 42-29 ka MIS 3 gravel, sand and peat, indicating warmest climate at the base and progressively cooler to the top. 1/9
The MIS 2 Fraser Glaciation, has two advance stades. These are advance glaciolacustrine sediments of the older Coquitlam Stade, a mix of laminated to finely bedded silt and sand and diamicton. 2/9
Indicates ice blocked the mouth of the Seymour valley, forming this lake. There is wood in these advance sediments, dating to around 21 ka. Implies there is a spruce-fir forest in the area as ice advanced. 3/9