Unit #3: Plate Tectonics and Volcanism
OBJECTIVES
• Analyze the interactions between the major systems (geosphere, atmosphere,
hydrosphere, biosphere) that make up the Earth.
– Compounds from the geosphere move into the atmosphere and hydrosphere
through volcanic eruptions.
• Explain, using specific examples, how a change in one system affects other Earth
systems.
– Volcanism can cause a temporary global cooling with secondary effects on the
atmosphere, hydrosphere and biosphere.
• Describe the Earth’s principal sources of internal and external energy (e.g.,
radioactive decay, gravity, solar energy).
– In the earliest stage of Earth’s history, internal thermal energy was generated from
gravitational force, the decay of radioactive elements and extraterrestrial impacts.
• Describe natural processes in which heat transfer in the Earth occurs by conduction,
convection, and radiation.
– Convection of heat in the Earth’s mantle is thought to drive the motion of plates.
• Explain how plate tectonics accounts for the features and processes (sea floor
spreading, mid-ocean ridges, subduction zones, earthquakes and volcanoes,
mountain ranges) that occur on or near the Earth’s surface.
• Explain why tectonic plates move using the concept of heat flowing through mantle
convection, coupled with the cooling and sinking of aging ocean plates that result
from their increased density.
– The main driving force of plate motion is gravity-controlled sinking of cooler, denser
oceanic lithosphere (as a limb of a convection cell) into subduction zones. The
subducting ocean lithosphere pulls the rest of the plate along with it.
• Describe the motion history of geologic features (e.g., plates, Hawaii) using
equations relating rate, time, and distance.
• Distinguish plate boundaries by the pattern of depth and magnitude of earthquakes.
• Use the distribution of earthquakes and volcanoes to locate and determine the types
of plate boundaries.
– Volcanoes are characterized by their size and shape and classified into three types
of landforms. Their form is controlled by magma chemistry and the plate tectonic
context.
• Describe how the sizes of earthquakes and volcanoes are measured or
characterized.
• Describe the effects of earthquakes and volcanic eruptions on humans.
• Explain how the chemical composition of magmas relates to plate tectonics and
affects the geometry, structure, and explosivity of volcanoes.
• Explain how volcanoes change the atmosphere, hydrosphere, and other Earth
systems.
– Biosphere as “other Earth systems.”
Unit #3: Plate Tectonics and Volcanism
VOCABULARY
biosphere
shield volcano
Stratovolcano/composite volcano
mid-ocean ridges
plate boundaries
mountain belts
mountain ranges
oceanic plates
plate tectonics theory
pressure
radioactive decay
sea floor spreading
subduction zones
tectonic plates
aging ocean plates
thermal energy
asthenosphere
conduction
plate collision
hot spot
molten rock/magma
transform faults
atmosphere
chemical composition of magma
cinder cone
continental collision
convection current
core
crust
density
earthquakes
explosivity
geologic features
geosphere
global positioning system
hydrosphere
lava
lithosphere
magmatic activity
mantle convection
radiation
viscosity
volcanoes