Glacier, which is advancing and the Margerie Glacier which is stable. The glacier thinning or retreating process is attributed to lesser incidence of snowfall on the hills, raising temperatures in the winter season followed by decrease in cloud cover and precipitation during the summer season. Post Little Ice Age Rebound in the Glacier Bay Basin has been studied by researchers of the Geophysical Institute, University of Alaska Fairbanks, Alaska in association with National Park and Preserve Service, under a National Science Foundation grant using GPS geodesy combined with studies of raised shorelines and tide gauges. The studies have established that the fastest rates of glacier rebound in the world are now taking place in the Glacier Bay region. The studies have also reported that "these adjustments to LIA loading and unloading are producing significant stresses on the earth's crust which can affect seismicity and regional tectonics. The rising land also is continually changing the geomorphic texture of shoreline throughout the Park and causing changes in hydrologic patterns, erosion, and sedimentation. All these changes have a direct impact on the ecosystems of the Park." Glacier Bay can be approached only by boats or ships and partly by hiking along three trails () and by kayaking along ) of shore line. The nearest road head and airport are in the small town of Gustavus, which is known as the southern gateway to the Glacier Bay. However, Gustavus as such is approachable only by air and sea. Juneau, the capital of Alaska, is about ). The approximate distance between Anchorage and Juneau is . The advancing and retreating characteristics of the glaciers in the Glacier Bay are explained in simple terms as a steady state of snow getting converted into ice on the hills. Ice, as a lens of water on the base of bedrock, slides by gravity downwards. The good moraine of rock and rubble insulates it from water erosion. As a result, during freezing temperatures that exists all the year, the glacier advances. When the insulation and erosion effect of the hills gets reduced erosion sets in and along with rising temperatures the glaciers start retreating. Another unpredictable phenomenon that is observed in many glaciers in the Glacier Bay is that of calving. Calving is a process in which blocks of ice get detached or break off from the glacier, irrespective of weather conditions, all the year round, and crash into