Download Section 1: Earth`s Interior (pages 16 – 24)

Study Guide Plate Tectonics (pages 16 – 47)
Extra help is available in the morning or at lunch! Just ask!!!!!
What do I need to Know?
- Vocabulary!
- Earth’s Interior Diagram (page 22 & 23)
- Convection in Earth’s Mantle (Figure 10 on page 27)
- Pangaea & Continents today (Figure 12 on page 30)
- Subduction (Figure 23 on page 38)
- Plate Tectonics (Diagram on pages 44 & 45)
*Don’t memorize the diagrams, rather understand what is happening!
Geology is the study of planet Earth. Geologists are the scientists who
study forces that make and shape planet Earth.
Geologists divide forces that change the surface (Continental Crust)
into two groups:
1. Constructive forces – shape the surface by building up mountains
and landmasses. Example: The island Surtsey was formed in the
Atlantic Ocean from a volcanic eruption.
2. Destructive forces – slowly wear away mountains. Example:
Ocean waves that wear away shorelines.
What’s inside Earth? Geologists can’t dig to the center of the
Earth. They use seismic waves study what’s inside Earth. Seismic
waves are vibrations that travel through Earth carrying the energy
from an earthquake. The speed and paths the seismic waves take
tell geologists how the planet is put together.
Three main layers make up Earth’s interior: (Be able to label layers!)
1. Crust – layer of rock that forms Earths OUTER surface.
- It includes both dry land and the ocean floor.
- The crust beneath the ocean is called oceanic crust.
- The oceanic crust consists mostly of dense rock called basalt.
- The continental crust (crust that forms the continents)
consists mainly of a less dense rock called granite.
2. Mantle – layer of hot, solid rock between the crust and core.
3. Core – consists of two parts:
- The outer core is a layer of molten metal (iron, nickel) that
surrounds the inner core. (Like a thick liquid)
- The inner core is a dense ball of solid metal (iron, nickel).
Earth’s Interior
The Earth’s molten (liquid) outer core is nearly as hot as the surface of
the sun. The heat from the outer core affects the mantle. How? Why?
- Heat is always transferred from a warmer substance to a cooler
substance. (Like touching a hot pot – the heat moved from the pot
to your hand).
- The movement of energy from a warmer object to a cooler object
is called heat transfer.
- There are three types of heat transfer:
1. Radiation – The transfer of energy through empty space.
Sunlight is radiation that warms Earth’s surface. Other familiar
forms of radiation are the heat you feel around a flame or fire.
2. Conduction – Heat transfer by direct contact of particles of
matter. Think about what happens as a spoon heats up in a pot of
soup. Heat is transferred from the hot soup and pot to the
spoon. If you touch the spoon, conduction transfers heat from
the spoon directly to your skin.
3. Convection –The transfer of heat by movements of a heated fluid.
- During convection heated particles of fluid begin to flow and
transfer heat energy from one part of the fluid to another.
- Heat transfer by convection is caused by differences of
temperature and density within a fluid.
- The differences in temperature and density cause convection
currents.
Convection in Earth’s Mantle
- Like soup simmering in a pot, Earth’s mantle responds to heat.
Convection currents have been moving inside Earth in the
asthenosphere for more than four billion years!
Continental Drift (Drifting Continents)
Alfred Wegener
- Hypothesized that all the continents had once been joined
together in a single landmass and have since drifted apart.
- Wegener named this supercontinent Pangaea meaning “all lands”.
- According to Wegener, Pangacea existed 300 million years ago.
- Over tens of millions of years, Pangea began to break apart. The
pieces of Pangaea slowly moved toward their present-day
locations becoming the continents they are today.
- Wegener’s idea that the continents slowly moved over Earth’s
surface became known as continental drift.
- Most scientist rejected this theory because he could not identify
a force that could move the continents.
Evidence to support Continental Drift
1. Landforms - Mountain ranges in South America match up to
mountains in Africa. Like putting a torn newspaper together
2. Fossils
3. Climate
Mid-Ocean Ridge
- Undersea mountain chain where new ocean floor is produced.
- Scientist mapped the mid-ocean ridge using Sonar.
Sonar is a device that bounces sound waves off underwater
objects and then records the echoes of these sound waves. (The
time it takes for the echo to arrive indicates the distance to the
object)
The mapping of the mid-ocean ridge made scientist curious to know
what the ridge was and how it got there.
Harry Hess, an American geologist was one of the first scientist
who studied the mid-ocean ridge.
- Harry Hess said that the ocean floors move like conveyor belts
beginning at the mid-ocean ridge.
- He said that at the mid-ocean ridge, molten materials rise from
the mantle and erupt. The molten material then spreads out
pushing older rock to both sides of the ridge.
- Hess called the process that continually ADDS new material to
the ocean floor sea-floor spreading.
Evidence to support Sea-floor spreading
- molten material
- magnetic stripes
- drilling samples
Now scientist asked, How can the ocean floor keep getting wider and
wider? The answer is that the ocean floor generally does not just
keep spreading. Instead, the ocean floor plunges into deep-ocean
trenches. Scientist found out that the ocean floor sinks back into
the mantle. This is called SUBDUCTION.
The Theory of Plate Tectonics
- Plate tectonics is the geological theory that pieces of Earth’s
lithosphere (PLATES) are in constant, slow motion, driven by
convection currents in the mantle.
- Plate tectonics explains the formation, movement, and subduction
of Earth’s plates.
- As the plates move, they collide, pull apart, or grind past each
other causing changes in Earth’s surface including volcanoes,
mountain ranges, and deep-sea trenches.
Faults – breaks in Earth’s crust where rocks have slipped past each
other.
Three types of Plate Boundaries
1. Transform boundaries
- Place where two plates slip past each other moving in opposite
directions. Earthquakes occur frequently along these boundaries.
2. Divergent Boundaries
- Place where to plates move apart
- Sea-floor Spreading happens here! As the two plates move away
from each other, magma wells up from the Earth's interior. It then hardens
into rock as it is cooled creating new ocean floor.
3. Convergent Boundaries
- Place where two plates come together
Visit this PBS website for a computer simulated look at types of
boundaries!
http://www.pbs.org/wgbh/aso/tryit/tectonics/intro.html