#yakutat

[fairyhelmet]

rainy days demand grooming 🌧️🦌

[highways-are-liminal-spaces]

Harlequin Lake trail in Yakutat, Alaska

[eopederson]

Snout of Hubbard Glacier, Yakutat, Alaska, 2025.

[grandboute]

Surfing spirit - Like a monday

C'est reparti !surfing

[ker-bee]

My biggest sockeye of the week. 

[earthstory]

Mt. St. Elias

The sharp peak at the top of this photo is the 4th highest peak in North America, Mt. St. Elias, with an elevation of 5489 meters (18,008 feet) above sea level. This mountain sits in a fascinating tectonic province, where the Alaskan coastline curves from northwest-southeast to east-west, and is found within the confines of Wrangell-St. Elias National Park. This part of Alaska has been assembled out of pieces of what we’d call exotic terranes. Today, the Pacific Plate is sinking into the mantle at the Aleutian subduction zone on Alaska’s south coast. Subduction has been occurring here for a long time; tens of millions of years, and it hasn’t always involved the Pacific Plate.

Sometimes, subduction zones or large volcanic outpourings can start in the middle of oceanic plates, giving rise to oceanic islands like those commonly found in the Western Pacific Ocean today. These chunks of crust sit high, above sea level, but they’re still sitting on oceanic plate that wants to subduct. If that oceanic plate subducts beneath a continent, the island arc will ride into the continent as though on a conveyor belt until it slams into the large landmass.

Island Arcs are usually big and buoyant enough that they don’t sink easily; instead they stick to the continent and break off, forming new land that we call an exotic terrane. Alaska has been assembled from a series of these collisions over tens of millions of years, and this park is home to several.

Wrangellia is a large oceanic plateau that accreted to North America approximately during the cretaceous. Closer to the shore from here sits another terrane, Yakutat, that accreted more recently.

As you might imagine, an island arc slamming into a continent is not a gentle process. These collisions tend to fold and fault rocks, building high mountain ranges. Mt. St. Elias sits right at the border between the Yakutat terrane and other provinces in Alaska and it is being pushed up rapidly as a consequence of these collisions and where it sits.

Literally just beyond the St. Elias peak sits a tongue of the Pacific Ocean. Across only a few kilometers of horizontal distance, the elevation changes from sea level to over 5000 meters. This dramatic change in elevation is about as large of relief change as there is at any location in the world, a testament to the fierce geologic forces at work in this park.

-JBB

Image credit: Richard Droker https://www.flickr.com/photos/29750062@N06/9565313424

Read more: http://www.amnh.org/explore/science-bulletins/earth/documentaries/moving-mountains/a-mountain-theory-on-the-rise http://www.nps.gov/wrst/planyourvisit/brochures.htm http://www.eos.ubc.ca/research/wrangellia/background.html

[oessa]

the textures of alaska / google earth

[highways-are-liminal-spaces]

Yakutat, Alaska and the Tsiu River