Plate Tectonics:
Earth's Dynamic
Puzzle
Plate tectonics is a fundamental theory in Earth science. It explains how our
planet's surface evolves over time. This process shapes continents, creates
mountains, and triggers earthquakes.
SL
by SHARON LASALA
The Earth's Ever-Changing
Surface
1
Ancient Earth
All continents were once joined in a supercontinent called
Pangaea.
2
Breakup
Pangaea began to break apart about 200 million years ago.
3
Present Day
Continents continue to move, shaping Earth's geography.
Continental Drift: The
Precursor Theory
ALFRED WEGENER
German scientist
who proposed the
theory of
continental drift in
the early 20th
century.
Jigsaw Puzzle
Wegener noticed
that continents
seemed to fit
together like puzzle
pieces.
EVIDENCE
He found matching fossils and rock formations on
different continents.
Wegener's Revolutionary Idea
Observation
Wegener noticed similarities between distant coastlines and
geological features.
Hypothesis
He proposed that continents were once connected and had
drifted apart.
Publication
Wegener published his theory in 1912, sparking debate in the
scientific community.
Plate Tectonics: The Modern Theory
Definition
Plates
Processes
Plate tectonics explains Earth's crustal
Earth's lithosphere is divided into large,
Plate interactions create mountains,
movements and geological processes.
rigid plates that move over time.
earthquakes, volcanoes, and ocean
basins.
Introduction to Plate
Tectonics
1
Earth's Structure
2
Plate Movement
The Earth's crust is divided
These plates constantly
into a mosaic of large plates
move and interact with each
known as tectonic plates.
other, driven by forces within
the Earth's mantle.
3
Geological Events
The movement of these plates leads to geological events such as
earthquakes, volcanic eruptions, and mountain formation.
The Far-Reaching Impact of
Plate Tectonics
1
3
Long-Term Process
2
Internal Heat
Plate tectonics operates over
Earth's internal heat drives
billions of years, shaping
plate movements and
Earth's surface.
related geological processes.
Ongoing Changes
Tectonic activity continues to shape our planet's environments and
landscapes.
This interaction of tectonic plates is
responsible for many different
geological formations such as the
Himalaya mountain range in Asia,
the East African Rift, and the San
Andreas Fault in California, United
States.
Types of Plate Boundaries
Convergent
Plates collide, forming mountains
or subduction zones
Divergent
Plates move apart, creating new
crust at mid-ocean ridges
Transform
Plates slide past each other,
causing earthquakes
Earth's Layers and Plate Movement
Lithosphere
Rigid outer layer composed of crust and uppermost mantle.
Asthenosphere
Partially molten layer beneath the lithosphere, allowing plate movement.
Core
Earth's hot center, driving convection currents in the mantle.
Causes of Plate Movement:
Convection Currents and
Mantle Dynamics
1
Heat from the Core
Heat from the Earth's core creates convection currents within the
mantle.
2
Mantle Convection
Hot, less dense material rises, while cooler, denser material sinks,
creating a circular flow.
3
Plate Movement
These convection currents drag the tectonic plates along, causing
them to move and interact.
Volcanic Activity and
Earthquakes at Plate
Boundaries
Volcanic Activity
Occurs at convergent and divergent boundaries, where magma rises
to the surface.
Earthquakes
Triggered by the sudden release of energy along fault lines, especially
at convergent and transform boundaries.
Geological Hazards
These events pose significant geological hazards to human
populations living near plate boundaries.
Mountain Building Processes:
Orogeny and Orogenesis
Orogeny
The process of mountain building, often associated with convergent plate boundaries.
Orogenesis
The geological processes that contribute to mountain formation, including folding, faulting, and
uplift.
Mountain Ranges
Result from the collision and deformation of tectonic plates, creating large-scale topographic
features.
Evidence for Plate Tectonics
Seafloor Spreading
Magnetic Striping
GPS Measurements
New crust forms at mid-ocean ridges,
Alternating magnetic patterns in oceanic
Precise measurements confirm ongoing
pushing plates apart.
crust record Earth's magnetic reversals.
plate movements.
The Pace of Plate Movement
1
Slow but Steady
2
Fingernail Growth
Plates move at rates of 2 to
Plate movement is
15 centimeters per year.
comparable to the speed at
which fingernails grow.
3
Significant Over Time
Small annual movements add up to major changes over millions of
years.
Plate tectonics shapes global landforms
and environments through the rock cycle,
mountain building, volcanism, and the
distribution of continents and oceans. These
phenomena, ultimately driven by Earth’s
internal heat, have far-reaching effects on
other parts of the Earth system, including
the sea level experienced along coastlines.