The great glaciers of the past carved these fjords, or drowned valleys, out of the moutains like great troughs. Landslides help widen the troughs as the glaciers remove the bedrock support on upper slopes. Huge icebergs may last a week or more, and they provide perches for bald eagles, cormorants, and gulls. Colors betray a berg's nature or origin. White bergs hold many trapped air bubbles.
Blue bergs are dense.
Greenish-blackish bergs may have calved off glacier bottoms. Dark-striped brown bergs carry morainal rubble from the joining of tributary glaciers or other sources. How high a berg floats depends upon its size, the ice's density, and the water's density. Bergs may be weighed down, submerged even, by rock and rubble. A modest-looking berg may suddently loom enormous and endanger small craft when it rolls over.