What do you notice about these two
pictures?
The Earth’s surface is
broken into rigid plates
that move in relationship to
one another.
Plate
tectonics is a theory that
describes the formation of
movements and interactions
between the tectonic plates.
What
is a theory?
 In
1912, a German scientist named Alfred
Wegener proposed a hypothesis called
continental drift.
 What is a hypothesis?
 He proposed that the continents had moved
or drifted apart over time.
 He studied this hypothesis his entire life, but
was never successful. He could not explain
how the continents had shifted over time.
 He did however, pave the way for plate
tectonics.
Theory that the continents have moved or
drifted over time from one location to
another.
Ice Age: Continental
Drift 
 In
the 1950’s and 1960’s scientists made
major discoveries about earthquakes and
volcanoes.
 These discoveries led to the theory of
plate tectonics.
 The
theory states that the continents are
embedded on plates. As these plates
move, they carry the continents with
them. Oceans are also a part of the plates.
 This theory is supported by knowledge
of important geologic processes
(earthquakes and volcanoes).
 Data
indicates that earthquakes and
volcanoes do not occur randomly. Instead
they are primarily located on plate
boundaries.
 The theory of plate tectonics helps to
explain this pattern.
 These plate boundaries are areas of high
heat flow, where molten rock moves upward
to Earth’s surface, causing volcanic activity.
A
mid-ocean ridge is a long chain of
volcanic mountains on the ocean floor
with a deep central valley.