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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
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Layered ash and cinders
Smallest volcanic cone
Short, narrow cone, steep sides
Violent eruptions
El Paricutin, Mexico
• Composite cones (stratovolcanoes)
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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