Geography The Northwest Passage How does the professor organize the information that she presents?

It was the promise of wealth that first drew European powers to look for a westward route to Asia. It was wealth rather than the idea of a New World that drove Columbus and other Europeans to search for a western route to China and Japan. However, they soon realized that the North American continent was a barrier to progress. So, they began to search for a way around the northern edge of the continent, a Northwest Passage that would link the Atlantic to the Pacific. For the next 500 years, they nudged their ships through the Arctic waters, looking for the Northwest Passage.
In the sixteenth century, the Spanish, Portuguese, French, and English all sent expeditions to the northern shores of North America. They were all driven back by the ice. The Englishman Martin Frobisher spent several years exploring what is now Canada and searching for wealth in the Arctic. He made three voyages in search of the Northwest Passage, and he did reach the mouth of the passage, but stopped when he found what he thought was gold. This "gold" turned out to be iron ore. In 1607, Henry Hudson began his exploration of the Canadian Arctic. He discovered the bay that later became Hudson Bay, but the voyage ended in tragedy when the crew rebelled. The Northwest Passage wasn’t crossed until almost 300 years later, when a Norwegian explorer completed the trip in three years.
The Northwest Passage is actually a number of possible routes through a deadly maze of sea ice, narrow straits, and oddly shaped islands. Today, icebreakers can follow the passage with ease, but to attempt it without this technology still requires a great deal of courage. Depending on ice conditions, one route might be open while another is blocked. The passage changes from year to year, and even from week to week.
In the summer of 2000, a Canadian Mountie took a large patrol boat into the heart of the Northwest Passage. He expected to encounter ice, but to his surprise, there were no bergs, no growlers, and no pancake ice. In fact, he found no ice at all. For the past few summers now, vast stretches of the Northwest Passage have been free of ice. The departure of the ice is the result of natural, long term atmospheric patterns that have warmed the Arctic in recent decades and also of the heating of the planet by greenhouse gases.
In the Arctic, temperatures have risen 3 to 4 degrees. That small difference has changed the landscape for thousands of miles. The ice has disappeared at a rate of about 3 percent each decade since the 1970s, and ice sheets that used to be ten feet thick are now less than six feet from top to bottom. Climate experts now predict that, in 50 years or less, the passage will be free of ice throughout the summer. Canadian officials say it’s only a matter of time before all kinds of ships—everything from supertankers to sailboats—will start crossing these once impassable waters.
There are potential consequences to shipping in the passage. Ships could disrupt the polar bears and bowhead whales that live there. There could be an increase in the smuggling of polar bear hides and walrus tusks. An increase in the number of tourists could mean an increase in the amount of trash they leave behind. The biggest concern, however, is the threat of an oil spill from a supertanker. An oil spill would damage this pristine region and be extremely difficult to clean up.