|470 N. Willow St.
Kenai AK, 99611-7707
|Air Traffic Manager:
Alaska is a big state. Contrary to weather maps and textbooks which often place Alaska in the little box in the corner of the nation's map, Alaska's size of over 586,412 square miles encompasses striking variations in terrain from the flat lowlands of the Yukon-Kuskokwim Delta to the highest mountain in North America, Mt. McKinley in the Alaskan Range. In acreage, Alaska equals the combined land area of the states of Wyoming, Montana, Washington, Oregon, Idaho, and Utah.
Alaska's landscape varies from a lush coastal forest to a treeless Arctic tundra, and it has complexes of mountains and ice fields that cover thousands of square miles. The climate ranges from brief cool summers and long dark winters in the Arctic to southern coastal areas where temperatures fall below zero only during the deepest winter months. Alaska has more square miles of land than people, and sixty percent of the population is located in the two urban areas of Anchorage and Fairbanks. Access to much of the State is by air or water, as the road network reaches only a small portion of the state.
Alaska is the westernmost extension of the North American Continent. Its east-west span covers a distance of over 2,000 miles and north-south a distance of over 1,100 miles. The state’s coastline is over 33,000 miles in length and is 50% longer than that of the conterminous U.S. In addition to the Aleutian Islands, hundreds of other islands, mostly underdeveloped, are found along the northern coast of the Gulf of Alaska, the Alaska Peninsula, and Bering Sea Coast.
Alaska contains 375 million acres of land and over three million lakes. There are twelve major rivers plus three major tributaries of the Yukon, all of which drain two thirds of the state's rivers. Four rivers, the Yukon, Alsek, Stikine, and Taku can be classed as major international rivers.
The two longest mountain ranges are the Brooks Range, which separates the Arctic region from the interior, and the Alaska and Aleutian Ranges, which extend westward along the Alaska Peninsula and the Aleutian Islands, and northward about 200 miles from the Alaska Peninsula and then eastward into Canada. Other shorter but important ranges are the Chugach Mountains, which form a rim to the central north Gulf of Alaska, and the Wrangell Mountains, which extend to the northeast of the Chugach Range and south of the Alaska Range. Both of these shorter ranges merge with the St. Elias Mountains, extending southeastward through Canada and across southeastern Alaska as the Coast Range. Numerous peaks in excess of 10,000 feet are found in all but the Brooks Range. The highest peak on the North American Continent, Mt. McKinley (20,320 feet above sea level), is also in Alaska. Several other mountains tower above 16,000 feet. Despite this, it is interesting to note that nearly all of the inhabited sections of the state are at 1,000 feet elevation or less.
Coastal waterways, a myriad of islands large and small, inlets, bays, and sounds make up Alaska's coastline. These, along with the Aleutian Islands, make Alaska a water-oriented state as evidenced by its fishing, tourist and cruise-ship industry.
Permafrost is a major factor in the geography of Alaska. It is defined as a layer of soil at variable depths beneath the surface of the earth in which the temperature has been below freezing continuously from a few to several thousands of years. It exists where summer heating fails to penetrate to the base of the layer of frozen ground. Permafrost covers most of the northern third of the state. Discontinuous or isolated patches also exist over the central portion in an overall area covering nearly a third of the state. No permafrost exists in the southcentral and southern coastal portions, including southeastern Alaska, the Alaska peninsula and the Aleutian Chain.
Earthquakes have long been a part of the earth's growing pains. However, most people are only dimly aware of the frequency and destructive power of an earthquake. As a matter of fact, the earth trembles sufficiently to produce a shock every thirty seconds on the average. Each year about a million quakes rock our planet. Of the earth's major earthquakes in just the past 75 years, the 1920 quake in Kansu, China, killed 180,000 people and 12 years later in 1932 at Kansu, another 70,000 lives were lost. More recently, the 1970 quake in Northern Peru killed 70,000. The Alaskan quake of March, 1964, severely damaged the cities of Anchorage, Seward, Valdez, Whittier, and Kodiak causing in excess of 500 million dollars in damages and loss of 115 lives.
One of the two major earthquake belts to girdle the earth is the ring of Fire, extending from Japan through the Aleutian Islands, the Alaska Range, and the western mountains of North America and South America. Earthquakes are not casual accidents but are part of the forces shaping the earth's features. Earthquakes are caused by the shifting of large plates of the Earth's crust, which are floating on the mantle of hot liquid rock which surrounds the hotter molten core of the Earth's center. As these plates move and shift together, they create great pressures on each other. As these pressures build, sooner or later, one or both of the plates let go, moves away from, or overrides the other plate. As the crust is squeezed together, and/or pulled apart, great tears, upheavals, bulges, etc. are created on the Earth's surface, along with a terrific shaking of the ground. Destruction can be great from an earthquake, to include the collapse of structures, bridges, freeways and roads, downed power lines, fire, flooding, uprooted trees, interruption of water services, runway and NAVAID destruction, etc.
A volcanic explosion is caused by exploding steam and gas and can be a most fearful natural outburst. Generally, these explosions are caused when fissures are opened by an impending eruption and ground water runs down and contacts the molten lava. The resulting steam can set off powerful explosions. Gas pressure up to six hundred times atmospheric pressure (9,000 PSI) hurls “bombs” out of volcanic craters at more than five hundred miles an hour. Many eruptions are preceded by numerous earthquakes. Heat is obviously involved in a volcano with hot gases, steam and molten rock which are all products of eruptions. The temperature of the earth increases with depth, and far below the surface there are sometimes great amounts of melted rock, or “magma,” at great temperatures and pressure.
Pressure tends to equalize, and magma follows the path of least resistance. If successful, it bursts forth as lava. Magma may also contain gas, as well as water or steam, in various quantities. The varying content of magma gives volcanoes their individual characteristics. In some cases, lava emerges from a volcano with little fuss and moves slowly over the surrounding country. Sometimes it bursts forth in an explosion, spewing rock, pumice, and ash high into the air. Great superheated clouds of gas may be ejected at tremendous pressure.
The most hazardous product of a volcano to aviation, other than the initial eruption, is the volcanic ash, called tephra. Tephra still in the air, or on the ground, causes major problems for aircraft. It is most abrasive in nature and can cause extensive damage to aircraft engines, pitting windscreens, sand-blasting aircraft surfaces, harming radio parts, landing gear parts, and air conditioning systems.
Active volcanoes in the Kenai area are Augustine, Mt. Redoubt, Mt. Iliamna, and Mt. Spur. Mount Redoubt ended a 24-year dormant period in December 1989 when it erupted violently, spewing ash over the Kenai Peninsula and as far away as Washington. A B747 approaching Anchorage from a polar route lost all four engines when it entered a cloud of ash, which the pilots saw but thought to be a common cloud. The engines were restarted but the aircraft incurred damage above $50 million(US).
Tsunamis do not just happen--they are caused. A tsunami is a traveling ocean wave that usually has its source in fairly deep water. These waves are believed to originate as vertically displaced columns of sea water, with submarine avalanches, displacement of the sea floor, and vibrations from volcanic and earthquake activity as the most likely causes. Their speed is controlled by water depth. As the waves enter shallower water speed diminishes but the wave height increases. Most often it is an earthquake that creates a tsunami by raising or lowering the ocean floor or by causing gigantic landslides beneath the sea. As the ocean floor drops away or rises up, great waves are generated which move for long distances until all the energy imparted to the water by the earthquake has been expended. Scientists are not positive about the exact mechanism of the generation of tsunamis, since they are produced miles below the surface of the sea, where it is difficult or impossible to know just what is happening. However, we do know much about what the waves do after they are generated. For one thing, they race at unbelievable speeds across the open sea. In such deep water a. tsunami can travel six hundred miles an hour. Once formed, the waves behave much like those caused by a stone tossed into a lake, moving outward in concentric circles until they strike a shoreline or die out across a sufficiently large body of water. On the open sea a tsunami may measure fifty miles from wave crest to wave crest and perhaps less than two feet in height, so that it is generally not noticed by passing ships. Depending on the forces that create them, tsunamis have periods ranging from five to sixty minutes and longer. There are generally from three to five major oscillations, or waves, coming within an hour or two. The waves then taper off, although it may be several days before normal sea conditions prevail. Earthquake ground motion sometimes generates waves at inland bodies of water such as lakes.
The climate of Alaska is as varied as its landscape. Temperatures can drop to -70 degrees Fahrenheit during the long winter, and rise into the 90's during the warm interior summer. Annual precipitation can range from less than 10 inches to over 200 inches. Geographic and climatic influences combine to produce wide variations in Alaska’s weather. Alaska can be divided into six climatic/topographic regions for aviation weather purposes:
Page Last Modified: 08/28/10 21:10 EDT
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