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Photo by Jon Major, USGS, 2007
Mount St. Helens has one of the world’s few growing glaciers, but this should not stop the concern for Earth’s rapidly changing cryosphere. By definition of National Geographic, the cryosphere contains the frozen parts of the planet. What is so important about glaciers? Approximately ¾ of all of Earth’s freshwater is stored in glaciers. These ice masses regulate global temperatures by the albedo effect, in which the ice reflects sunlight allowing the Earth to retain less heat. Ice sheets and glaciers regulate sea levels and weather. They keep the water cycle under control and provide fresh drinking water. Earth’s ice goes through many cycles and changes caused by many factors including human-caused climate change and volcanic eruptions. The planet is currently undergoing a state of rapid change.
Volcanic eruptions can cause a rapid or instant loss of glaciation. Prior to May 1980, the Fraser Glaciation period of the Pacific Northwest allowed huge masses of ice to develop on the side of Mount St. Helens. This volcano’s high cone, at approximately 9,667 feet, resulted in the development and permanence of new alpine glaciers, with approximately 13 glaciers on the flanks of the mountain, and numerous perennial snow fields. The famed landslide on Sunday, May 18th, 1980 destroyed or melted 70% of the volcano’s glacier mass. Melting glacier water mixed with much of the volcanic material released that day and caused lahars (volcanic mudflows) to flow down the river valleys. Lahars carried so much water and volcanic material that wiped out bridges and homes along the Toutle River valley.
Between the eruption itself, and the preceding events in which the glaciers melted away, we see the destructive side to these magnificent features of Earth. However, the Earth has ways of replenishing itself. It was only after the eruption that the massive crater we see in the volcano today was formed. In the 1980-86 lava dome building eruptions, a glacier formed in the valley between the crater wall and the newly formed dome. This glacier, now called the Crater Glacier, is famed for being one of the few glaciers on Earth currently growing in size. With the shadow cast on this ice field from the crater wall and the rocky debris that offers protection for most of the year, it is a perfect environment to nourish a growing glacier. With our ever-changing planet and receding ice area, Mount St. Helens is a rare occurrence of growing ice.
By Lily Black
