Rudyerd Bay, Misty Fjords National Monument

Rudyerd Bay, Misty Fjords National Monument

by | Oct 2, 2021

Rudyerd Bay is a deglaciated fjord in the Coast Range of Southeast Alaska in Misty Fjords National Monument, about 89 miles (143 km) north-northwest of Prince Rupert and 39 miles (63 km) northeast of Ketchikan, Alaska. The fjord extends northeast for 11.5 miles (19 km) from the east shore of Behm Canal, with two significant branches. The first is Punchbowl Cove on the south shore about 2.7 miles (4 km) into Rudyerd Bay, and it extends southeast for 2.2 miles (3.5 km). The second is an unnamed fjord at about 7.6 miles (12 km) into Rudyerd Bay, and it extends south-southeast for about 3.0 miles (5 km). The Coast Range is a massive batholith, the largest single body of granitic rock in North America, that formed during the Coast Range Episode that began 115 million years ago during the mid-Cretaceous period. Misty Fjords National Monument is a wilderness area administered by the U.S. Forest Service as part of the Tongass National Forest. John Muir during his travels to Alaska, went through the Coast Range on the Stikine River and compared the region with Yosemite Valley for its similar geology and glacial morphology. Light-colored granite, about 50 to 70 million years old, has been sculpted by glaciers into deep U-shaped valleys. Many of the glacial valleys are filled with seawater and are called ‘canals’. The walls of these valleys are near-vertical and often rise 2,000 to 3,000 feet (600 to 900 m) above sea level, and descend to 1,000 feet (300 m) below sea level.

The Misty Fjords area was historically inhabited by Tlingit, Tsimshian, and Haida people, and possibly even by Tsetsaut Athabascan people. Over thousands of years, they made over 50 pictographs on the rock walls of the fjords. These were made with red ochre, a mixture of hematite and clay, and were probably intended at signboards marking territory or significant events. At least one Tlingit village was present when the region was visited in 1793 by Captain George Vancouver, the first European to explore Behm Canal, a natural channel about 108 miles (174 km) long separating Revillagigedo Island from the mainland. Vancouver traded peacefully with inhabitants of a village in the Behm Canal, but on the following day, they were visited by several canoes. After a peaceful exchange, the natives tried to steal items from the yawl. A woman in the stern of the largest canoe encouraged the warriors to throw spears. Two of the British seamen were injured, but by successfully defending their position, Vancouver’s boats were able to escape. Vancouver continued charting Behm Canal and later named the fjord in honor of Magnus von Behm, who was the governor of Kamchatka in 1779 when Captain James Cook’s ships, with Vancouver among the crew, arrived at Petropavlovsk shortly after Cook was killed in Hawaii. It was Behm who carried the news of Cook’s death to Europe. Vancouver discovered New Eddystone Rock, a column of basalt 237 feet (72 m) tall in the middle of Behm Canal. Rudyerd Bay was named in 1879 by William Healey Dall of the U.S. Coast and Geodetic Survey for the English engineer, John Rudyerd, who rebuilt the Eddystone lighthouse in England after its destruction in 1703. In 1980, the Alaska National Interest Lands Conservation Act set aside the Misty Fjords National Monument as part of a settlement between the federal government and the State of Alaska over land use. Misty Fiords is 2,294,343 acres (928,488 ha) within Tongass National Forest and all but 151,832 acres (61,444 ha) are designated as wilderness. The portion not in the wilderness area was reserved for potentially mining the Quartz Hill molybdenum deposit, possibly the largest such mineral deposit in the world. The site was first discovered in 1974. The ore body is massive in form reaching 11,089 feet (3,380 m) long, 6,866 feet (2,093 m) wide, and 1,601 feet (488 m) thick. The mineralization at this location is from the Oligocene epoch (33.90 to 23.03 million years ago) to the Miocene epoch (23.03 to 5.33 million years ago).

The Coast Mountains encompassing Misty Fjords National Monument are a series of major mountain ranges extending from southwestern Yukon through the Alaska Panhandle and virtually through all of British Columbia south to the Fraser River. These mountain ranges consist of deformed igneous and metamorphosed structurally complex pre-Tertiary rocks that originated from diverse locations around the globe. The first formation event began 130 million years ago when a group of active volcanic islands riding on a tectonic plate called the Insular Plate, approached a pre-existing continental margin and coastline of North America. These volcanic islands were formed by subduction of the former Farallon Plate under the Insular Plate during the early Paleozoic era. The Insular Belt was then welded onto the pre-existing continental margin by magma that eventually cooled to form a large mass of igneous rock, and creating a new continental margin. The Farallon Plate continued to subduct under the new continental margin supporting a new continental volcanic arc called the Coast Range Arc about 100 million years ago during the Late Cretaceous period. Magma rising from the Farallon Plate under the new continental margin ascended through the newly accreted Insular Belt, injecting huge quantities of granite into older igneous rocks of the Insular Belt. This molten granite burned through the old oceanic sediments creating a glittering metamorphic rock called schist. The older intrusions were then deformed under the heat and pressure of later intrusions, turning them into a layered metamorphic rock known as gneiss. In some places, mixtures of older intrusive rocks and the original oceanic rocks were distorted and warped under intense heat, weight, and stress to create unusual swirled patterns appearing to have been nearly melted into a liquid in the process. Volcanism along the entire length of the Coast Range Arc shut down about 50 million years ago and many of the volcanoes disappeared by erosion. What remains of the Coast Range Arc today are outcrops of granite formed when magma intruded and cooled at depth beneath the volcanoes, forming the present Coast Mountains of Misty Fjords National Monument. Read more here and here. Explore more of Rudyerd Bay here:

About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2022 (bottom). Each stripe represents the average global temperature for one year. The average temperature from 1971-2000 is set as the boundary between blue and red. The color scale goes from -0.7°C to +0.7°C. The data are from the UK Met Office HadCRUT4.6 dataset. 

Credit: Professor Ed Hawkins (University of Reading). Click here for more information about the #warmingstripes.

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