In this monthly feature, we span the globe to examine Our Changing Landscape with time series of medium resolution RapidEye satellite imagery. The RapidEye archive dates back to late 2008 and already contains more than 4 billion square kilometers of data. This month, we look at the changes in summer snow cover on Mount Saint Helens from year to year..
The RapidEye Constellation
RapidEye is a constellation of five 5-meter medium resolution satellites each offering five spectral bands of information. The RapidEye constellation offers a daily revisit time to every location on the planet with a huge footprint that is 77-km wide. The data is priced competitively with a base price of $1.28 per square kilometer for all five spectral bands – academics do receive discounts. RapidEye adds a fifth band, the red edge, to the ‘traditional’ multispectral set of blue, green, red and near-infrared (NIR). The additional spectral data available in the red edge band allows users to extract more useful land ‘information’ than can be from traditional 4-band imagery sources. When RapidEye imagery is ordered as a Level 3A Orthorectified product, images from multiple dates are extremely well registered, making it the ideal data source for Our Changing Landscape.
Mount Saint Helens
One of America’s most iconic mountains, the snow-capped Mount Saint Helens was formed starting 275,000 year ago and is now the most active volcano in the Cascade Mountain Range. During its long history, Helens has seen periods of relatively abundant volcanic activity, for instance during the Smith Creek Eruptive Period (approximately 2,000 BCE to 1,350 BCE) and most recently the Modern Eruptive Period which started May 18, 1980. Each eruption changed the shape, size and appearance of the conical volcano. Today, Mount St. Helens stands 8,363 feet tall.
On March 16, 1980, the first signs of renewed volcanic activity, i.e. a series of small earthquakes, were evident in Mount Saint Helens. On March 27th, a steam jet exploded through the ice cap and within a week, the crater grew to more than 1,300 feet across. By May 17th, more than 10,000 earthquakes rattled the peaks and the north flank had visibly expanded by at least 450 feet. The volcanic activity culminated on May 18, 1980 with a massive eruption that spewed rocks, ash and lava out of the dome. The huge blast triggered a 3.7 billion cubic yard landslide which trimmed the height of the volcano by some 1,314 feet. The eruption cloud reached 80,000 feet in less than 15 minutes, spreading 1.4 billion cubic yards of ash across the Earth in just 15 days. The blast leveled 4 billion board feet of timber, 27 bridges and nearly 200 homes as well as killed 57 people. After the May 18th blast, Mount Saint Helens saw 21 more eruptions over a 7 year period. After laying dormant from October 1986 to late 2004, the volcano was active again from September 23, 2004 until 2008.
Mount Saint Helens is not active today and since the activity in 2008, forests and wildlife around the caldera have recovered. In the series of RapidEye images that follow, you can see changes in the volcano, particularly the amount of summer snow which waxes and wanes from year to year.
If you would like to find out more about using RapidEye for your academic studies, engineering projects or any landscape analysis, let us know at [email protected] or (303) 993-3863.