In order to analyze the meteorological evolution of Augustine Island, Alaska, it is also important to understand the dynamic geology that is not only characteristic of volcanoes but of coastal Alaska in general. Volcanoes actually enabled the atmosphere we have today from outgassing, or the emission of dissolved gasses from molten rocks. With our range of 100 million years into the past and future, it is difficult to theorize about the weather of Augustine because it did not exist 100 million years ago. Alaska is essentially a compilation of drifting tectonic plates from Asia and other locations of the Pacific, which is why it is riddled with the Archipelagos and beautiful fjords. The geology of coastal Alaska is difficult to map because of this, as there are many types of rock that clearly came from different locations.
The above images show the original collison of Alaska, then part of Eastern Asia, with the North American Plate. It is this collision that essentially dictated and continues to play an important role in the topography and climate of the Aleutian Range and South Central Alaska. To begin, we will look at the current geography of Augustine Island as well as the current climagraph to serve as a reference for the hypothesized past and
future projections.
Augustine is indicated by the red dot in the Kachemak Bay/Cook Inlet area of South Central Alaska, and sits at 59 degrees 21' 48" N, & 153 degrees 26' 00" W. As discussed previously, this location experiences a maritime climate and is subject to the Aleutian Low in the winter, and just on the edge of the Pacific High in the summer. This makes it susceptable to winter mid latitude cyclones, which are nearly equivelant to hurricanes in tropical climates. Below is a climagraph that represents the average temperature and precipitation for the bay area where Augustine is located.
http://climate.gi.alaska.edu/climate/Climographs/ADQ.html
Again, the temperature in the summer months rarely reaches above 70, and can be freezing throughout the winter. This is a relatively extreme change in temperature that much of the 30 degree-60 degree North latitude zone experiences. Not only is this influenced by the pressure systems, but the latitude gives it an extremely low angle of illumination by the sun in the winter and therefore contributes to the low winter temperatures. With that in mind, we can begin to understand how millions of years ago a somewhat different climate existed. Below is an image of how earths continental plates looked approximately 105 million years ago, in the Cretaceous Period of the Mesozoic Era, "The Age of Reptiles".
Again, the temperature in the summer months rarely reaches above 70, and can be freezing throughout the winter. This is a relatively extreme change in temperature that much of the 30 degree-60 degree North latitude zone experiences. Not only is this influenced by the pressure systems, but the latitude gives it an extremely low angle of illumination by the sun in the winter and therefore contributes to the low winter temperatures. With that in mind, we can begin to understand how millions of years ago a somewhat different climate existed. Below is an image of how earths continental plates looked approximately 105 million years ago, in the Cretaceous Period of the Mesozoic Era, "The Age of Reptiles".
Much of what scientists hypothesize about Alaska's climate 100 million years ago is based on geologic discoveries. For example, plant fossils were discovered that suggested Alaska's climate would have been similar to present day Northern California, Oregon, & Washington. Below is what a climagraph may have looked like for that time period. As the graph illustrates, temperatures were warmer at that time and were slightly closer to maritime tropical than todays cooler climate. The precipitation remains high in the late summer months and early fall, and is fairly consistent throughout the year, as it is today. This would correlate with the explosion of flowering plants on earth and the thriving of reptiles. Although, unlike today, Augustine would not have experienced the orographic protection of the Aleutian Range as the Islands are not fully merged with the North American Continent, therefore leaving the eastern side of the Aleutians vulnerable at this point in time.
Despite not having the topographic protection of being in a bay as the island is today, the climate was clearly much more mild and so it would not have been subject to the winter cyclones. In addition, it would have received more precipitation throughout the year because unlike today, it would have been apart of the Aleutian Chain instead of lying to the east and receiving protection.
Although it is difficult to discern from the image, what used to be Augustine Island would most likely be part of the inland topography 100 million years from now. There are many patterns in the geologic history our earth, some of which we have discussed, that support this hypothesis. First, the U.S.G.S. puts Augustine Island at a slightly higher latitude in the Pleistocene Epoch, which when compared to the location of the developing Aleutian Archipelago in the Cretaceous Period, this shows that the island is moving north. If this continued, and as it appears on the projection map, the island will eventually become part of the mountain range in the mainland. This will transition Augustine from having a coastal maritime climate to a continental climate, lacking the moist, oceanic influence that it received for millions of years. Based on this theory, below is a climagraph that may represent Augustine's location in the distant future.
As the graph illustrates, it will now be influenced by a Continental Air Mass, much more dry than the Aleutian Low that originates over the North Pacific. In addition, the average winter temperatures will be much colder as the latitude will have had increased much more significantly. The winter months will therefore receive even less light from the sun, coupled with the reduced moisture to hold in warmth, the climate of Augustine is becoming more like the Arctic than the Pacific Northwest. It is even possible that this area could be covered in ice, if the earths pattern of glaciation continued. To gain a more photographic perspective of this interesting transition from 100 million years ago to 100 million years into the future, below is a series of photographs from each of the three time periods.
100 Million Years Ago-Pre Augustine Island
Present: Augustine Volcanoe
100 Million Years From Now: Part of the Interior Mountain Range
Although we have an idea of how the earth has evolved and will evolve, as well as recent data on temperature and global weather changes, the earths dynamic nature makes it difficult to be sure about theories stretching 100 million years into the future. There is still much to be learned about the geologic past of earth, and science will need to evolve as we uncover more. It is difficult to predict the local weather of the front range, let alone 100 million years into the future, however in making an attempt to do so we can learn much about the way our atmosphere and pressure systems influence the climates of our planet.
Additional Sources:
Tarbuck, Lutgens, Tasa. Earth: An Introduction To Physical Geology. Tenth Edition.
2011. Pearson. New Jersey.
No comments:
Post a Comment