Kachemak Bay, Alaska: An Exploration of People and Place

Where are We?
Who are We?
What are the Dynamic Forces that Shape Our Place?
Volcanoes
Tides, Winds, Weather
Earthquakes
Geology
Glaciers
How Have We Survived?
What are the Challenges of Living Here?
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Pratt Museum:  Homer Society of Natural History Pratt Museum logo:  kayak, fish, whales

Blue Glaciers - Patient Earthmovers

Glaciers, slow rivers of ice, have scoured and shaped Cook Inlet and Kachemak Bay. Unlike their dynamic sidekicks, the violent and unpredictable earthquakes and volcanoes, glaciers are patient earthmovers. These blue giants begin with the fall of snowflakes. Winter upon winter, ice age cold prevented melting. Under pressure, snowflakes compacted to become millions of interlocking ice crystals. Over time their own weight causes glaciers to flow downhill, bulldozing as they go. As glaciers retreat, they shrink in size because more ice is melting, but the ice continues to flow downhill.

Since the first ice mass crept southward several million years ago, the waltzing advance and retreat of glaciers have sculpted Kachemak Bay. Their movement contoured mountains, set the course of rivers, left bench lands, deposited the Homer Spit, and gouged U-shaped valleys, such as Tutka Bay and Sadie Cove.

Chunk of Grewingk glacier floating in Grewingk lake
Grewingk Glacier
© Bill Scott

Landlocked Grewingk Glacier still shimmers above Kachemak Bay. Today, it has retreated 3½ miles inland, is about 13 miles long, and covers 30 square miles. It was first mapped and measured by William Healy Dall in 1880.

Collapse in Time - Grewingk Glacier

Glacier meets and melts into a glacial lake
Before the Landslide
Enoch (Ed) Nordby Collection
Pratt Museum Photo Archives

In October 1967, a huge landslide collapsed into the lake below Grewingk Glacier. It carried enough mountainside to fill eleven million dump trucks - a wedge of earth and rock 2,000 feet tall, half a mile wide, and more than 600 feet deep. A forceful wave roared across the glacial flats toward Humpy Creek - knocking down trees and tumbling icebergs.

The whole flood plain was full of icebergs. Some were Volkswagen sized. A lot of them had been rolled so that they were round.
-Al Davis, Homer
The glacier itself was the culprit. During recent advances, it ground away rock and undercut the mountainside. According to the Homer News, when the ice receded, nothing remained to hold the mountain. It was like pulling a bookend from a crowded shelf. Experts say it could happen again - this week or in a thousand years.
Thousands of trees and bushes went into the bay. It messed up the whole Inlet. Fishermen caught them in their nets. Dead wood, alders, spruce - everything went into the bay.
-Yule Kilcher

Icebergs flood the water
After the Landslide
Austin Post, US Geological Survey

Shaping the Homer Spit

The Homer Spit, formed about 15,000 years ago, is a terminal moraine - gravel bulldozed by a glacier and left behind during the retreat of the last ice age. The Spit reaches only part way across the Bay. In the deeper waters of the south side, the ancient glacier's floating icy tongue never touched bottom, leaving no moraine.
How Glaciers Carved the Bay Videofor kids!
dial-up broadband
An animated Claymation® film, produced by local students, shows the formation of Kachemak Bay.
Graphic showing glacial formation of Kachemak Bay
Formation of Homer Spit
Drawing by Richard Reger

 

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