As the earth travels around the sun, different regions receive more direct sunlight than others. The tilt of the earth on its axis is responsible for the different seasons in the northern and southern hemispheres. In the summer, when the North Pole is tilted toward the sun, the northern hemisphere gets more direct sunlight and the days are longer than during spring, fall and winter. In winter, the tilt is away from the sun and sunlight strikes the northern hemisphere at a lower angle. Latitude is what determines both the length of the day and the angle of the sun (Waterton/Glacier International Peace Park is pretty far north and straddles the 49th parallel along the Canadian border). The amount of sunlight striking the earth’s surface (solar insolation) and the length of the day are determined by the position of the sun in the sky. The reduced amount of winter sunlight striking the earth due to shorter days and angle of the sun causes colder temperatures. As the land and its air mass cools, surface waters turn to ice and precipitation freezes to cover the land with snow.
At northern latitudes and in mountainous terrain, winter comes early and stays late. At higher elevations the atmosphere is thinner and holds less warmth. Consequently, it’s colder, snow lasts longer, and the length of the growing season is greatly reduced. Elevations in Glacier range from less than 3,200 feet in the Lake McDonald valley to 6,646 at Logan Pass, to more than 10,000 feet on the tallest mountains in the park. In Glacier National Park, the seasons are jokingly referred to as “June, July, August and winter.” There is some truth to this as the high country may be snow-free for only about 3 months of the year. It is not unusual to see visitors skiing at Logan Pass in June and occasionally even into July. Winter lasts a long time throughout most of the park.
Lamp or flashlight
Have students draw a picture of the Earth and sun. Labeling with an X the part of the Earth where it would be summer and an O showing the parts of Earth where it would be winter. Write 2-3 sentences describing why we have different seasons in Montana. Also students should answer the question, "What will the weather be like in Montana next season?" giving evidence about the sun and Earth to back up their answer.
This activity will help the students understand that all places have winter, but winters in places like Glacier National Park and northwest Montana are a lot different from places farther south. In Montana, we get a greater degree of darkness and cold than in other places in the world. This is why it is important that our animals and plants have adaptations to survive the winter.
Have students locate the following places on the globe: Santiago, Chile; Belem, Brazil (at the mouth of the Amazon); and Fairbanks, Alaska. Discuss how weather/seasons would be different in these locations throughout the year.