Christine Miller, age 11, of Albany, New York, for her question:
How are fiords formed?
Scenic f iords adorn the coasts of Norway, Alaska, Chile and several other lands. They were created by a very complex set of circumstances, involving ice and ice ages, land and sea. They are fairly recent geological features and most of them were formed during the past million years. But people who live near them, hope that their beautiful fiords will remain for ages to come.
The coastline of Norway is a fringe of rocky fingers, dotted with rocky offshore isles. The ocean bites long, deep bays between the fingers. Long ago the people of Norway named them fjords or fiords. The ragged coastline of Alaska also is carved with long fiords and there are more along the coast of Chili. These deep estuaries along certain rocky shores share the same geological history, because the same geological factors worked together to carve and form them.
The major factor is ice, the massive ice of moving glaciers. Glaciers, of course, were most plentiful during the ice ages. Their remnants still remain as the ice fields of Alaska and the icecaps on many lofty mountains at high altitudes. All glaciers, past and present, are immensely heavy masses of ice pressing down on the earth's crust, and they move in strange ways, somewhat like streams and water flowing in slow motion.
During the ice ages, the pressure and the movements of glaciers remodeled the surface of the earth. Their ice was frozen moisture that failed to join the rivers and, thus, did not take its normal course back to the oceans. As the mighty glaciers increased, the global sea level became lower.
Fiords were formed when the land areas were somewhat larger and the earth was shaped by massive, moving glaciers. Glaciated valleys tend to be long troughs, gouged deeper than the valleys of tributary streams, and they carry the main river which is fed by streams tumbling down from terraces higher up the slopes.
Fiords are unusually deep U shaped troughs that dip down to the shore and under the sea. Waterfalls and streams often cascade from high down their steep sides. They are typical glacial valleys, carved when the region suffered the hardships of crushing sheets of ice. The movements of glaciers are measured with probing sticks and very delicate instruments. An existing glacier may move only a feoy inches a year or perhaps even many miles. But it does not move together as a single, solid unit. At the surface, the sides and center creep along at different speeds, and the surface moves at a different speed from the deeper ice. Through thousands of years, these various motions carved out vast glaciated valleys. Fiords were formed when these glaciers cut through thick layers of dense rock along the coasts and beaches. Later, the sea level rose and flooded them.
Glaciation carved the U shaped fiords. Their depth and location was determined by the thickness and weight of the glaciers, as well as the glacier's slopes and motions. Another factor was the carvability of rocky layers. Glacial erosion, including melting snow and the scraping at the bottom of the massive ice, also played a major role in forming the fiords.