Shuyak Island Natural History
Geology
Shuyak Island’s substrate is comprised mainly of rock from either
volcanic or marine sedimentary origins. A small band of intrusive
granitic rock runs from the northern part of the island near Carshan
Point to the southwest corner near Shuyak Harbor. Glaciers covered Shuyak Island until about 10,000 years ago. The
island’s intricate coastline is a result of the presence of these
glaciers. Soils on Shuyak, as throughout the rest of the Kodiak area, are
shallow and low in organic materials. An average cross section of soil
would show a thick, slightly decomposed layer of organics at the top,
followed by a thick layer of ash. The ash is a result of the eruption of
Mt. Katmai in 1912 that showered the Kodiak area with up to 18 inches of
ash. Following the ash layer there is usually a deep layer of decomposed
organics followed by a layer of weathered rock or unconsolidated
materials. The portion of Shelikof Strait between the Alaska Peninsula and
Shuyak/Afognak Islands has potential for petroleum production. This
petroleum province is considered a continuation of the oil and gas
producing Cook Inlet basin.
Flora
Shuyak Island’s plant communities are best described in two general
forms:
- Forested areas dominated mature Sitka Spruce stands; and
- the outer coast, dominated by a variety of alpine plants
associated with much higher elevations.
A total of 238 plant species representing 54 families has been
recorded within the park. Forested areas are located inland and along protected waterways.
Sitka spruce may have spread to Shuyak and/or Afognak Islands from the
Kenai Peninsula about eight hundred years ago. Shuyak and Afognak
Islands have the oldest trees, while much of Kodiak Island remains
treeless. Thick Layers of moss and a variety of shade tolerant shrubs
make up the understory of Shuyak's mature spruce forests. The state originally classified land on Shuyak as "timber lands." In
1968 the state scheduled a timber sale in Big Bay. Five qualified
bidders responded to the sale and one was selected. However, the sale
did not go through because the bid price was below the appraised value
of the timber. Botanists refer to studying the vegetation of the park's outer coast
as "alpine botany at sea level." The alpine species are well suited for
the exposure to the area's brutal storms. These small, ground-hugging
plants probably established themselves shortly after the glaciers
retreated. The outer coast areas are not exclusively the domain of
alpine plants, however. Some small and sturdy Sitka Spruce trees grow in
protected areas of the outer coast and a few plant species that are
tolerant of saltwater grow near the high tideline and along shallow
estuaries.
Fauna
Four of the six land mammals native to the Kodiak Island group are
found in the park. These are the brown bear, little brown bat, tundra
vole and river otter. In addition to the native species, a number of
mammals introduced to the Kodiak Archipelago are found in the park. They
are: the Sitka black-tailed deer, muskrat, red squirrel, Arctic ground
squirrel and beaver. The Arctic ground squirrel has only been observed
on Dark Island.
While the boundaries of the park do not include saltwater habitats
used by sea mammals, these animals are commonly encountered during a
visit to the park. The most common sea mammal observed around Shuyak
Island, the sea otter, was almost completely removed from the Kodiak
area by hunting pressure during the 1800's and early 1900's. Subsequent
protection through federal law has resulted in a population rebound for
the otter. An estimated 13,200 occupy water in the Kodiak Island area.
It is believed that because otters were not as heavily hunted in the
North Afognak and Shuyak area, this population served as the source from
which the pods are slowly repopulating areas to the south. Other sea mammals that spend all or part of the year in the saltwater
surrounding the park are: harbor seals, sea lions, dall and harbor
porpoises, and minke, fin, killer, gray and humpback whales. Harbor
seals regularly haul out in the northwest corner of Big Bay and along a
line of rocks east of Green Island.
Weather & Local Climate Information
Shuyak Island’s maritime climate is similar to that found throughout
the Kodiak Archipelago. Cool temperatures, moderate precipitation and
cloudy skies are typically experience year round.
Annual precipitation averages 67 inches at the Kodiak weather
station. Data collected at the Big Bay ranger station from June through
September 1991-1993, indicates that Shuyak Island is generally cooler
and wetter than Kodiak is during those months. Storms occur throughout
the area frequently. February storms are the most frequent and intense
while July offers calmer weather with the lowest frequency and intensity
of storms.
Foggy conditions prevail from July through September when the air
contains the most moisture and is warmer than the ocean. Clouds obscure
an average of 70% of the sky through the year in Kodiak. Complete
overcast conditions occur slightly less than half of the time.
The prevailing winds around Shuyak Island are northeast except in
spring and late summer when they shift to southwest and west. Sustained,
extreme wind speeds at weather reporting stations around the Kodiak
Archipelago range from 50-75 knots with gusts as high as 100 knots.
To time recreational activities for the best possible weather, most
people visit the park during the summer months. Few people venture to
Shuyak between January and March, when fierce storms mean travel to and
from the island can be restricted for weeks. However, any visitor
whether they arrive by boat or plane must plan for weather delays due to
the unpredictable nature of the area’s weather.
