Formation of the earth’s
• Geosphere formed by accretion and
• Surface stays molten for millions of years
• Continents formed as crust cooled
• Over time geologist have theorized what
the continents looked like over the last 500
Wegener’s Continental Drift
• All continents were once joined together as a
supercontinent called Pangea
– Similar shorelines
– Fossils on opposite coasts match
– Mountain ranges end on one continent and pick up on another
– Same age rocks found on separate continents
– Climate changes seen in the development of coal deposits
– Glacial deposits found on South America and Africa
– No mechanism for the changes.
Finding A Mechanism
• Wegener’s data was very well accepted but
without a mechanism the theory was abandoned
• In the early part of the 20th century the
development of sonar enabled scientists to see
the terrain of the ocean floor
• The discovery of the mid ocean ridge and the
spreading of the sea floor helped to bring about
the development of the currently accepted
Plate Tectonic Theory
• The crust is broken into pieces and is
moved by the movement of the
asthenosphere below it….
• What causes the asthenosphere to move?
Properties of Materials
• First we must understand the properties of
– What is a solid?
• Holds a shape
• Molecules are tightly packed together
– What is a liquid?
• Takes the shape of its container
• Molecules are more loosely collected and can move
• Ability to flow from one container to another
– What is a gas?
• Expands to fill the container
• Molecules are widely spaced
• Can flow, expand and be compressed
Is it a solid or a liquid?
• Use these two substances and determine the properties
of each ….
• Silly putty
• Cornstarch (mix 3 Tablespoons of cornstarch with 1 T of water – the
mixture should be very hard to stir but will flow out of a cup – if it
gets too watery add a little more corn starch)
• Go ahead and watch the podcast that I have on how this looks it will
• Go ahead and do the exploration now…it will make the
rest of the lecture make more sense – Besides its FUN!!!
Properties of Layers
• Crust – solid – conducts heat
• Upper Mantle – solid with liquid
properties – convects heat
• Lower Mantle – solid rock –
• Outer Core – liquid metal (less
pressure than inner core allows
metal to melt)
– Liquid convects heat
• Convection is the movement
of heat as a flow of molecules
• Inner Core – solid iron and nickel
with strong nuclear fusion
producing intense heat
– Solid conducts heat
• conduction is the movement
of heat from molecule to
Convection in Asthenosphere
• Heat from core changes
the density of the
• As temp rises density
decreases and fluid rises
• As temp decreases,
density rises and fluid
• This movement is called
a convection current
which moves the
asthenosphere and thus
the crustal plates
attached to it.