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Volcanoes continued Volcanic Landforms: Cones Mauna Loa, Hawaii • Shield volcanoes Multiple layers of basaltic lava Shallow sides due to magma’s low viscosity “Gentle” eruptions • Cinder cones Layered ash and cinders Smallest volcanic cone Short, narrow cone, steep sides Violent eruptions El Paricutin, Mexico • Composite cones (stratovolcanoes) Layered ash, lava, and mud Steep sides due to magma’s high viscosity Tall volcanoes – 1 to 2 miles high Violent eruptions Mount St. Helens, WA Volcanic Landforms: Flood Basalts • Large (10-100 square miles) outpourings of very low viscosity basaltic lava • Multiple, “quiet” eruptions • Lava plateau forms Flood basalt volcanism has been connected to major mass extinction events in the past. Volcanic Landforms: Calderas Volcano rapidly empties its magma chamber, and support is lost. Overlying material collapses into magma chamber: a caldera forms. • Explosive calderas Silica-rich magma feeding these volcanoes has high viscosity; gases tend to become trapped at high pressure within the magma, resulting in explosion. • Non-explosive calderas Basaltic magma feeding these volcanoes is silica poor and much less viscous; the magma chamber is drained by large lava flows rather than by explosive events. Crater Lake, Oregon Hot Spot Volcanism Hot spots are due to a plume of hot magma flowing up to the crust from the core-mantle boundary. This plume is for some reason sustained over long geologic periods. Over time, the tectonic plates of the Earth move over these hot spots leaving a trail of volcanoes. Yellowstone Caldera ~10 MYA Pacific plate movement ~15 MYA 630,000 YA ~5 MYA How do volcanologists predict eruptions? • Measuring small quakes – increase in number & intensity before eruption. • Measuring slope – bulges may form with magma pushing up. • Measuring volcanic gases – outflow of volcanic gases (sulfur dioxide, carbon dioxide) may precede eruption. • Measuring temperature from orbit – monitoring changes in temperature over time. THE HYDROSPHERE Water, the most exciting substance on Earth • Water is the only substance that naturally exists as solid and liquid and gas. • Water is the substance that is necessary for any form of life as we know it. • The Earth’s liquid water constitutes the hydrosphere. Water on Earth • Total amount of water on Earth is ~1,386,000,000 cubic kilometers (km3) or about 366,000,000 trillion gallons (which is NOT a lot…think apple skin ). • Liquid water covers 71% of the Earth's surface. • Water is a Heat Storage: specific heat of water is 5-fold higher than that of stone or sand; sunlight penetrates deep into the water but only the surface of stone, clay, or sand. • Water is constantly moving on, above and below the surface of the Earth through the hydrologic (water) cycle which involves water transport and phase changes by the following physical processes: evaporation, transpiration, condensation, precipitation, surface runoff, and infiltration. The Hydrologic (Water) Cycle The water cycle is driven by the Sun and involves the exchange of energy in the form of heat. Water Cycle Components water vapor rising ocean, lake, river Evaporation heated by the Sun, liquid water changes to water vapor over bodies of water Transpiration release of water vapor from plants and soil Water Cycle Components Water body Warm air Condensation water vapor cools and changes to droplets of liquid water in the air Precipitation rain, snow, hail, sleet, etc. Water Cycle Components Infiltration water filters from the surface into the ground Surface Runoff water flows across the land