Sunday, August 13, 2017

Katmai National Park and the Alaska Peninsula

This morning The World is docked in Dutch Harbor Alaska on Unalaska Island in the Aleutian chain. Dutch Harbor was attacked in World War II and eleven Americans lost their lives in the bombing. We will visit the World War II Museum here later today.

We have enjoyed generally good weather on this trip and it is my pleasure to share more photos with you. This posting has less geology and more nature - the Brown bears we saw at Geographic Harbor in Katmai National Park were phenomenal.

This is part of the ruins of Ft. Abercrombie on Kodiak Island. When Kiska Island was taken by the Imperial Japanese Army, the American military fortified many of the other Aleutian Islands in the Pacific. Ft. Abercrombie was one of these fortifications. It is now an Alaska State Park.

Kodiak Island is the 2nd largest island in the United States (Hawai'i is the largest) and contains the extreme northern end of the North American temperate rain forest. The southern-most edge of this rainforest is found way down along California's Big Sur coast.

They do green like the Colorado Plateau does red! Mosses cover the branches of a Sitka spruce tree in the State Park.

Ferns in the rain forest on Kodiak Island.

A road cut in the town of Kodiak exposed deep water marine sediments that are part of the Chugach terrane. See my previous posting for a simple description of terrane geology. A more detailed and scientific description of the Church terrane can be found here. Generally, these rocks were deposited in a deep marine trench like the nearby modern Aleutian trench. These sediments are Late Cretaceous to Eocene in age, about 75 to 55 million years old.

The World at anchor at the mouth of Geographic Harbor in Katmai National Park, Alaska Peninsula.

 Entrance to Geographic Harbor and a slow Zodiac cruise to the inside of the harbor.

Foliated intrusive rocks are part of the volcanic complex here.

Note the dark-colored bedrock in the peak and the light-colored talus slopes below it. The lighter material is volcanic ash from the June 6, 1912 eruption of the Novarupta volcano, located about 20 miles north of this spot. The 1912 eruption of Novarupta is considered the largest volcanic eruption on Earth during the entire 20th Century and is surpassed in all of recorded history only by the 1815 eruption of the Tambora volcano in Indonesia. It covered a nearby valley in over 300 feet of pyroclastic material. Even though no one was nearby to record the events of this eruption, modern-day volcanologists with more tools have revealed the sequence of events that occurred here during the 60 hours of eruption. It is now one of the best studied volcanic eruptions known. You can read more about the eruption and its aftermath here (and in the contained links).

In Geographic Harbor, it was difficult to focus on geology as no fewer than nine bears were ambling along the shoreline in this relatively small area.

Close-up of the mother bear seen above. The species is known as the American brown bear (Ursus arctos horribilus), the silver tip bear, or the grizzly bear. They did not seem so fierce when viewed from the safety of a boat.

Viewing bears safely from a Zodiac. They hardly even noticed us quietly sitting out in the water. about 75 meters away It would have been a much different feeling had we been walking ashore or camping here.

Katmai National park boasts nearly 2,200 bears in its 4 million acres.

Another mother with her two cubs digging for amphipods in the tidal mud.

This cub is about 7 months old. Anyone wanting to see Brown bears in their native habitat got what they wanted on this trip. Next stop - the Semidi Islands.

Zodiacs ready for a landing at the Semidi Islands.

We climbed up to a pass on the island that allowed us to view its rocky shore. Geologically, these islands are a southwest extension of the Chugach terrane and of Kodiak Island.

Close-up of shoreline.

This coast suffers the brunt of harsh winter storms from the open Pacific Ocean. Huge driftwood logs were thrown-up on the shore of cobble beach. In the distance some 10,000 miles is the shoreline of Antarctica, the next bit of land in that direction.

This is Rose root (Rhodiola rosea). My colleague Conrad Field made the identification for me and I was surprised how important this plant is to Artic peoples for medicinal purposes. Check out the link above.

Horned puffins (Fratercula corniculata) can be found on these islands. They nest here but spend up to seven months on the open water in winter.

Next stop is the Shumagan Islands and the island of Unga (ninth largest island in the US). We stopped in Delarof Harbor at an abandoned fishing village that provided a great palette for photography.

This is the grave of a young girl who likely died in the influenza epidemic of 1918.

Church steeple in Unga. The village was last inhabited in the 1970s and served as the base for a cod fishery before abandonment.

Two Great horned owls (Bubo virginianus) in a Sitka spruce tree in the village of Unga.

A yellow paintbrush (Castilleja unaleschcensis) is a common wildflower in this part of Alaska.

The World at anchor near the east shore of Unga Island. There is a gold prospect on this island that is gearing ups for operation. So far, 150,000 ounces of gold have been taken from here (in historic time) and the new venture may yield much more. Read about it here.

A northern sea otter (Enhydra lutris kenyoni) rests in the quiet waters of the bay.

Near the outside of Delarof Harbor are these fantastic shapes.

Rock and The World.

A final stop was made on Unimak Island, the easternmost of the Aleutian chain. The Isanotski volcano stands at 8,104 feet above sea level as viewed from Otter Cove looking to the northwest.

Zodiac and The World in morning light in Otter Cove on August 12, 2017.

Bear trackway on the sand at Otter Cove.

This has been a wonderful voyage on The World. Thanks to all of the residents here who make my visit with them possible.

Sunday, August 06, 2017

Expedition to the Alaska Peninsula and Aleutian Islands

I am taking a "break" from rainy Arizona and gone to sunny Alaska. (No, that is not a typo). As northern Arizona is experiencing one of the wettest monsoons ever, I arrived in Anchorage Alaska to clear sunny skies. Go figure.

I am back on board The World, perhaps the most unique ship that sails the Seven Seas. I am here to give geology lectures and drive Zodiacs as we cruise this amazing, tectonically active terrane.

I have already given one lecture entitled, "Fiery Bridge of the North: The Geology of the Alaska Peninsula and the Aleutian Islands." I include some slides from that lecture here, as well as some fabulous photos of the volcanoes we sailed past on August 5 in the Cook Inlet after leaving Anchorage.

Slides from my lecture: "Fiery Bridge of the North: The Geology of the Alaska Peninsula and the Aleutian Islands"

Title slide

Letting people know what the subject is about. The Colosseo lecture Hal is phenomenal and has been updated since the last time I was here. Images are projected on a center screen from an overhead projector and on two TV monitors left and right of that. All lectures are streamed into the apartments and videos of each lecture becomes archived on board and are instantly retrievable for no less than three years.

I used this annotated Digital Elevation Map (DEM) to introduce listeners to the geography and landforms of Alaska. By pressing the advance key, the individual names of features appear as I talk about them. The two mountain ranges shown, the Alaska Range and the Brooks Range, determine the course of the Yukon River as it makes its way from the interior to the coast.

A colorized DEM shows the Aleutian volcanic arc and the 25,000 foot deep Aleutian trench. The Pacific Ocean floor is being consumed under the arc as it moves to the northwest (toward the upper left) into the trench. When that slab arrives about 60 miles deep, it is the right temperature to begin melting and blobs of magma move upward to create the volcano arc.

Don't be confused by the spelling of the word "terrane' above. While the more common spelling "terrain" refers to the shape of the land or a description of the landforms on it, geologists use "terrane" to refer to discrete blocks of crust that have different histories and origins to rocks in adjacent blocks. The rock type, age and place of origin are different between the various colors  The idea is that each colored area originated elsewhere and by plate tectonic processes drifted towards and arrived to North America in a giant collision, much like Australia is today drifting north to attach the Indonesian archipelago to it.

All of this drifting of "exotic terranes" means that earthquakes happen here and I spent some time describing the Great Alaskan Earthquake of March 27, 1964. This iconic image was taken that fateful afternoon when a 9.2 magnitude earthquake struck about 150 miles southeast of Anchorage. It is still the 2nd most powerful quake recorded in historic time and 143 people lost their lives (# 1 is the earthquake that struck Valdivia Chile in May, 1960). Most fatalities were not from shaking of the ground but by the tsunami waves that emanated from the rupture, some as far away as Oregon and California. This photo was taken on 4th Street in Anchorage looking east across Barrow Street.

So what did I do with some free time in Anchorage - I went to the exact same spot to rephotograph the same location. I was surprised to see that the Muti-storied building in the distance was still standing today and was a welcomed reference point. During the lecture, I scrolled back and forth from one image to the other, giving a sense of the destruction that the earthquake had wrought. A stream in Anchorage is to the left and the gaping hole seen in the previous photo formed when the land slumped downward into the stream valley.

It's all fine to talk about things like this but most people want to know the answers to the questions posed above. That is when geology becomes relevant to lay persons - "What does this mean for me?" So I then mentioned that after the quake, the US Geological Survey sent three geologists to Alaska to figure out what happened. Remember that 1964 was the infancy of plate tectonic theory and many aspects of it had not yet been determined. But using some preliminary thoughts on the subject, these geologists ultimately cored into the fault zone to see if a history of rupturing could be determined. The cores revealed the following information.

This is a photograph of a part of a sediment core obtained about nine feet below the surface and near the coast to the southeast of Anchorage. It revealed a two-part lithology, with marine clay below abruptly ending at and covered in terrestrially derived peat.The organic matter in the peat was radiocarbon dated at about 2,800 years ago, showing the moment in time when this mega-quake occurred. An idea was formulated that areas near the coast that were below sea level  before the quake were uplifted when the ruptured happened, while areas further inland near Anchorage, subsided after the rupture. The diagrams below explain this further.

Map showing areas of uplift and subsidence during the Great Alaskan Earthquake of 1964. The star shows the epicenter of the rupture.

During an approximate 600 year period, the lower slab moves north (right) and tugs at the overriding plate. Friction keeps the two slabs coupled tight, causing subsidence near the coast but uplift inland.

In mere minutes, the upper plate breaks free from the friction of the lower plate and recoils south (left). The frictional pressure is released causing an earthquake and the coastal areas become uplifted relative to their former position while inland areas subside. A mechanism and explanation had been uncovered!

Next I moved on to the topic of Alaskan volcanoes and gave listeners a great tool for discovering the story of Alaskan volcanoes.

The Alaska Volcano Observatory is the place to go for everything about Alaskan volcanoes.

And now some pictures from sailing in the Cook Inlet at sunrise on August 5.

Sunrise over the water. I have provided links to each volcano mentioned here on the AVO web site. Check them out for a more complete picture of each volcano.

Early morning light on the Redoubt volcano.

The light changed quite quickly.

This is Mt. Spurr, another volcano with the power to shut down the skyways when it sends up a puff of ask. Thirteen volcanoes line the coast of the Cook Inlet.

Iliamna volcano.

Augustine volcano in late eventing light as we sail toward Kodiak Island.

The Barren Islands as fog creeps northward from the Pacific Ocean on the opposite side. Thanks for reading!