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This lesson is designed to explore some of the colorized SIR-C images of volcanoes around the world. The color assignments for each of the images are listed below with the image description. Note that similar colors between images do not necessarily mean the same thing. For example, forested areas may appear blue on one image and greenish on another. The assignments of colors is subjective and they need to be interpreted for each image. However, colors do serve to bring out subtle features and they do make each image easier to interpret.
Look in the directory called /Data/Mods1to5/Module04/Images/Volcano. The following files should be in the directory for this lesson:
The other eight Decade Volcanoes are:
An explanation of these images follows.
ColimaMx.gif (268.gif) - This is a SIR-C image of the Colima volcano in Jalisco, Mexico, a vigorously active volcano that erupted as recently as July 1994. The eruption partially destroyed a lava dome at the summit and deposited a new layer of ash on the volcano's southern slopes. Surrounding communities face a continuing threat of ashfalls and volcanic mudflows from the volcano. This image was acquired SIR-C/X-SAR on October 1, 1994. The image is centered at 19.4 degrees north latitude, 103.7 degrees west longitude. The area shown is approximately 35.7 kilometers by 37.5 kilometers (22 miles by 23 miles). The summit area appears orange and the recent deposits fill the valleys along the south and southwest slopes.
Color Assignments:
GaleVolc.gif (162K GIF) - This SIR-C radar image of the area surrounding the Galeras volcano in southern Colombia shows the ability of a multi-frequency radar to map volcanic structures that can be dangerous to study on the ground. Galeras has erupted more than 20 times since the area was first visited by European explorers in the 1500s. Volcanic activity levels have been high in the last five years, including an eruption in January 1993 that killed nine people on a scientific expedition to the volcano summit. Galeras is the light green area near the center of the image. The active cone, with a small summit pit, is the red feature nestled against the lower right edge of the caldera (crater) wall. The city of Pasto, with a population of 300,000, is shown in orange near the bottom of the image, just 8 kilometers (5 miles) from the volcano. The image was acquired on April 15, 1994. North is toward the upper right. The area shown is 49.1 by 36.0 kilometers (30.5 by 22.3 miles), centered at 1.2 degrees north latitude and 77.4 degrees west longitude. The radar illumination is from the top of the image.
Color Assignments:
MaunaLoa.gif (276K GIF) - This SIR-C radar image is of the Mauna Loa volcano on the Big Island of Hawaii. Mauna Loa has erupted more than 35 times since the island was first visited by westerners in the early 1800s. The large summit crater, called Mokuaweoweo Caldera, is clearly visible near the center of the image. Leading away from the caldera (towards top right and lower center) are the two main rift zones shown here in orange. Rift zones are areas of weakness within the upper part of the volcano that are often ripped open by new magma (molten rock) as it approaches the surface at the start of an eruption. The most recent eruption of Mauna Loa was in March and April 1984, when segments of the northeast rift zones were active.
If the height of the volcano is measured from its base on the ocean floor instead of from sea level, Mauna Loa is the tallest mountain on Earth. Its peak (center of the image) rises more than 8 kilometers (5 miles) above the ocean floor. The South Kona District, known for cultivation of macadamia nuts and coffee, can be seen in the lower left as white and blue areas along the coast. North is toward the upper left. The area shown is 41.5 by 75 kilometers (25.7 by 46.5 miles), centered at 19.5 degrees north latitude and 155.6 degrees west longitude. The image was acquired on October 2, 1994. The radar illumination is from the left of the image. The color combinations in this radar image are caused by differences in surface roughness of the lava flows. Smoother flows, called pahoehoe flows, are depicted in red, and rougher flows, called a'a flows in volcanology terminology that originated in the Hawaiian language, are shown in yellow and white. Hawaii's other most active volcano, Kilauea, is located off to the right of Mauna Loa and is not visible in this image.
Color Assignments:
MRainier.gif (323K GIF) - This is a SIR-C radar image of Mount Rainier in Washington state. The round cone at the center of the image is the 14,435-foot (4,399- meter) peak of Mount Rainier. The volcano last erupted about 150 years ago and numerous large floods and debris flows have originated on its slopes during the last century. Today the volcano is heavily mantled with glaciers and snowfields. More than 100,000 people live on young volcanic mudflows less than 10,000 years old and, consequently, are within the range of future, devastating mudslides. This image was acquired on October 1, 1994. The area shown in the image is approximately 59 kilometers by 60 kilometers (36.5 miles by 37 miles). North is toward the top left. In addition to highlighting topographic slopes facing the space shuttle, SIR-C records rugged areas as brighter and smooth areas as darker. The scene was illuminated by the shuttle's radar from the northwest so that northwest-facing slopes are brighter and southeast-facing slopes are dark. Forested regions are pale green in color; clear cuts and bare ground are bluish or purple; ice is dark green and white. On the lower slopes is a zone of rock ridges and rubble (purple to reddish) above coniferous forests (in yellow/green). The western boundary of Mount Rainier National Park is seen as a transition from protected, old-growth forest to heavily logged private land, a mosaic of recent clear cuts (bright purple/blue) and partially regrown timber plantations (pale blue). The prominent river seen curving away from the mountain at the top of the image (to the northwest) is the White River, and the river leaving the mountain at the bottom right of the image (south) is the Nisqually River, which flows out of the Nisqually glacier on the mountain. The river to the left of the mountain is the Carbon River, leading west and north toward heavily populated regions near Tacoma. The dark patch at the top right of the image is Bumping Lake. Other dark areas seen to the right of ridges throughout the image are radar shadow zones.
Color Assignments:
Rwanda.gif (408K GIF) - This is a SIR-C radar image of Central Africa, showing the Virunga volcano chain along the borders of Rwanda, Zaire and Uganda. The image was acquired on October 3, 1994. The area is centered at about 2.4 degrees south latitude and 30.8 degrees east longitude. The image covers an area 56 kilometers by 70 kilometers (35 miles by 43 miles). The dark area at the top of the image is Lake Kivu, which forms the border between Zaire (to the right) and Rwanda (to the upper left). The steep cone in the center of the image is Nyiragongo volcano, rising 3,465 meters (11,369 feet) high, with its central crater now occupied by a lava lake. Nyiragongo has small craters and cones on it's flanks. To the right of Nyiragongo is the cone of Nyamuragira volcano, which is 3,053 meters (10,017 feet) tall, with radiating lava flows dating from the 1950s to the late 1980s. In the center left of the image is the Virunga volcanic field, home to the endangered mountain gorillas. These active volcanoes constitute a hazard to the towns of Goma, Zaire and the nearby Rwandan refugee camps, located on the shore of Lake Kivu at the top left. This radar image highlights subtle differences in the vegetation of the region. The green patch to the center left of the image in the foothills of Karisimbi is a bamboo forest where the mountain gorillas live. The vegetation types in this area are an important factor in the habitat of mountain gorillas.
Color Assignments:
Unzen.gif (210K GIF) - This is a SIR-C radar image of the area around the Unzen volcano, on the west coast of Kyushu Island in southwestern Japan. Unzen, which appears in this image as a large triangular peak with a white flank near the center of the peninsula, has been continuously active since a series of powerful eruptions began in 1991. The image was acquired on April 15, 1994 and shows an area 41.5 kilometers by 32.8 kilometers (25.7 miles by 20.3 miles) that is centered at 32.75 degrees north latitude and 130.15 degrees east longitude. North is toward the upper left of the image. The radar illumination is from the top of the image which is why the north flank of Unzen appears particularly bright in this image. The city of Shimabara sits along the coast at the foot of Unzen on its east and northeast sides and other settlements dot the coast along the whole peninsula. A dome of thick lava at the summit of Unzen has been growing continuously since 1991. Collapses of the sides of this dome have generated deadly avalanches of hot gas and rock known as pyroclastic flows. These flows have killed several people since this most recent eruption began.
Color Assignments:
Taal.gif (355K GIF) - This is a SIR-C radar image of Taal volcano, near Manila on the island of Luzon in the Philippines. The black area in the center is Taal Lake, which nearly fills the 30-kilometer-diameter (18-mile) Taal caldera. The caldera rim consists of deeply eroded hills and cliffs. The large island in Taal Lake, which itself contains a crater lake, is known as Volcano Island. The bright yellow patch on the southwest side of Volcano island is the site of an explosion crater that formed during a deadly eruption in 1965. The image was acquired on October 5, 1994 and shows an area approximately 56 kilometers by 112 kilometers (34 miles by 68 miles) that is centered at 14.0 degrees north latitude and 121.0 degrees east longitude. North is toward the upper right of the image. Since 1572, Taal has erupted at least 34 times. Since early 1991, the volcano has been restless, with swarms of earthquakes, new steaming areas, ground fracturing, and increases in water temperature of the lake. Volcanologists and other local authorities are carefully monitoring Taal to understand if the current activity may foretell an eruption. The bright area in the upper right of the image is the densely populated city of Manila, only 50 kilometers (30 miles) north of the central crater.
Color Assignments:
| Teacher's Guide - Table of Contents |
Converted to the IBM-PC by Al Wong, sirced03@southport.jpl.nasa.gov
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena, CA 91109
