![]() The measurement involves determining the velocity of the falling sphere. If the fluid has a low viscosity, it offers less resistance to flow, so the ball falls faster. This makes sense: if the fluid has a high viscosity it strongly resists flow, so the sphere falls slowly. The faster the sphere falls, the lower the viscosity. This exercise uses one of the oldest and easiest ways: we will simply see how fast a sphere falls through a fluid. There are many ways to measure viscosity, including attaching a torque wrench to a paddle and twisting it in a fluid, using a spring to push a rod into a fluid, and seeing how fast a fluid pours through a hole. As expected, hawaiian volcanoes erupt more fluid lavas (called basalt) than do the Cascade volcanoes, which erupt a lava called andesite. Thus, shield volcanoes like we have in Hawai'i have gentle slopes (less than 10 degrees), while stratovolcanoes like the Cascades in the northwestern mainland are much steeper (roughly 25 degrees). Also, the more viscous the magmas a volcano erupts, the steeper the volcano. The more viscous the magma, the fatter the lava flow. Viscosity also affects the shapes of lava flows and the mountains they erupt from. ![]() On the other hand, when more viscous (higher viscosity) lavas do erupt, they usually do so explosively. The more fluid a magma, the more likely it is to erupt. In fact, one of the major differences between styles of mashed potatoes is the viscosity of the starchy mass: some people like their potatoes running and teeming with milk and butter (they are fans of low-viscosity potatoes), while others like their potatoes drier and stickier, so they almost crack rather than flow (these people are devoted to high-viscosity potatoes). For example, pushing a spoon with a small force moves it easily through a bowl of water, but the same force moves mashed potatoes very slowly. Viscosity is an internal property of a fluid that offers resistance to flow. To determine how fluid a liquid really is by measuring its viscosity. These fluid lava flows can flow great distances from vents in either pāhoehoe and ‘a‘ā forms, although fissures sometimes erupt blocky lava flows.Teacher Page: Viscosity Hawai'i Space Grant Consortium, Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, 1996 While lavas of any compositions may be erupted from fissures, basaltic lava flows are common. USGS-Field-trip guide to Columbia River flood basalts, associated rhyolites, and diverse post-plume volcanism in eastern Oregon USGS-Field-trip guide to the vents, dikes, stratigraphy, and structure of the Columbia River Basalt Group, eastern Oregon and southeastern Washington USGS-Columbia River Basalt Stratigraphy in the Pacific Northwest Nez Perce National Historical Park, ID, OR, MT, WA. Manhattan Project National Historical Park, NM, WA, &TN. Lewis and Clark National Historical Park. Lake Roosevelt National Recreation Area. ![]() John Day Fossil Beds National Monument, Oregon. Hagerman Fossil Beds National Monument, Idaho. ![]() Parks Containing or Near Rocks of the Columbia River Basalt Groupįort Vancouver National Historic Site, Washington. The dike swarms that are the source of the Columbia River Basalts have a north-northwest orientation, with fissure lengths reaching as much as 110 miles (180 km).Ĭolumbia River Basalts are found in several NPS sites in the Northwest including Nez Perce National Historical Park, John Day Fossil Beds National Monument, Lake Roosevelt National Recreation Area, and Manhattan Project National Historical Park. They were erupted from fissures, mostly in eastern Oregon, southeastern Washington, and Idaho, and accumulations of lava flows up to 13,000 ft (4,000 m) thick filled much of the Columbia Basin, with lava flows traveling as far as the Oregon-Washington coast. They were erupted within a short time period, mostly between 16.7 and 15.5 million years ago. The Columbia River Basalts are flood basalts (or plateau basalts) meaning that they are thick accumulations of lava flows that were erupted within a short period of time and that cover a vast geographic area.Ĭolumbia River Basalts cover more than 81,000 square miles (210,000 square km), and have an estimated volume of 50,000 cubic miles (210,000 cubic km). The Columbia River Basalt Group is the product of the largest eruptions in North America’s history. ![]() Kīlauea and Mauna Loa are large shield volcanoes with extensive rift zones on their flanks where fissure eruptions can occur. Lava fountaining reached heights of 150 ft (45 m) and built a spatter cone. A fissure eruption on Kīlauea Volcano’s Lower East Rift Zone in 2018. ![]()
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