![]() ![]() Cinder Cones (Spatter Cones)Ĭinder cones, like Mt. This is largely because of the presence of pyroclastic eruptive material, which is not strong. If volcanic activity ceases, it might erode away within a few tens of thousands of years. Click the image for more attributions.įrom a geological perspective, composite volcanoes tend to form relatively quickly and do not last very long. Sources: Karla Panchuk (2017) CC BY 4.0 Top photo by Simon Matzinger (2014) CC BY 2.0 view source. Bottom: Diagram of a composite volcano showing alternating layers of lava and tephra. Top: Cotopaxi in Ecuador exhibits the upward-steepening cone characteristic of composite volcanoes. Fuji in Japan, which erupts basaltic lava. This results in volcanoes of smaller diameter than shield volcanoes. ![]() Composite volcanoes typically erupt higher viscosity andesitic and rhyolitic lavas, which do not travel as far from the vent as basaltic lavas do. The change in the slope reflects the accumulation of tephra fragments near the volcano’s vent. Cotopaxi displays the characteristic shape of composite volcanoes, which have slopes that get steeper near the top of the volcano. The layers (strata) is where the alternative name, stratovolcano comes from. Bottom- Karla Panchuk (2017) CC BY 4.0 Composite Volcanoes (Stratovolcanoes)Ĭomposite volcanoes, like Cotopaxi in Figure 11.24 (top), consist of layers of lava alternating with layers of tephra (blocks, bombs, lapilli, and ash Figure 11.24, bottom). Bottom: Diagram of a shield volcano island, showing the build up of basaltic lava flows. Top: The Sierra Negra volcano in the Galápagos Islands exhibits the low, rounded shape characteristic of shield volcanoes. The low viscosity of the lava means that it can flow for long distances, resulting in the greater size of shield volcanoes compared to composite volcanoes or cinder cones.įigure 11.23 Shield volcano. Shield volcanoes, like the Sierra Negra volcano in the Galápagos Islands (Figure 11.23, top), get their gentle hill-like shape because they are built of successive flows of low-viscosity basaltic lava (Figure 11.23, bottom). Cinder cones have straight sides, unlike upward-steepening composite volcanoes, or rounded shield volcanoes. It rises 172 m above the landscape, and has a diameter of under 500 m. Eve Cone is a cinder cone on the flanks of Mt. Unlike shield volcanoes, composite volcanoes have a distinctly conical shape, with sides that steepen toward the summit.Ĭinder cones are the smallest, and almost too small to see next to a volcano like Mauna Loa. Composite volcanoes tend to be no more than 10 km in diameter. It rises 1,356 m above the surrounding terrain in the Cascade Range of the western United States, and has a diameter of approximately 6 km. ![]() Helens is shown on the left of Figure 11.22. Kīlauea Volcano rises only 18 m about the surrounding terrain, and is almost not visible in the scale of the diagram, however it still stretches over a distance of 125 km along the eastern side of the Island of Hawai‘i.Ĭomposite volcanoes are the next largest. Kīlauea Volcano is also a shield volcano, albeit a much flatter one. Source: Karla Panchuk (2017) CC BY 4.0 modified after Steven Earle (2015) CC BY 4.0 view original Straight-sided cinder cones are the smallest, and barely visible in the scale of the diagram. Broad, rounded shield volcanoes are the largest, followed by cone-shaped composite volcanoes. Figure 11.22 Comparison of volcano sizes and shapes. In total, Mauna Loa is a 17,170 m thick accumulation of rock. Furthermore, the great mass of the volcano has caused it to sag downward into the mantle by an additional 8,000 m. It rises up from the ocean floor at a depth of approximately 5,000 m. The summit of Mauna Loa is presently 4,169 m above sea level, but this represents only a small part of the volcano. Figure 11.22 shows the largest of all shield volcanoes- in fact, the largest of all volcanoes on Earth- Mauna Loa, which makes up a substantial part of the Island of Hawai‘i and has a diameter of nearly 200 km. Shield volcanoes, which get their name from their broad rounded shape, are the largest. Figure 11.22 illustrates the size and shape differences amongst these volcanoes. There are three types of volcanoes: cinder cones (also called spatter cones), composite volcanoes (also called stratovolcanoes), and shield volcanoes. Individual volcanoes vary in the volcanic materials they produce, and this affects the size, shape, and structure of the volcano. The products of volcanism that build volcanoes and leave lasting marks on the landscape include lava flows that vary in viscosity and gas content, and tephra ranging in size from less than a mm to blocks with masses of many tonnes. ![]()
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