Kodo Millet PPT made by Ghanshyam bairwa college of Agriculture kumher bhara...
HPU NCS2200 Plate Tectonics Lecture 1
1. Formation of the earth’s
surface
• Geosphere formed by accretion and
density stratification
• 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
billion years….
2.
3.
4.
5.
6.
7. Wegener’s Continental Drift
Theory
• All continents were once joined together as a
supercontinent called Pangea
• Evidence:
– 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
• Problem?
– No mechanism for the changes.
8.
9.
10. Finding A Mechanism
• Wegener’s data was very well accepted but
without a mechanism the theory was abandoned
for decades
• 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
theory.
11.
12.
13. 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?
14. Properties of Materials
• First we must understand the properties of
materials
• http://www.youtube.com/watch?v=3qAs1Nt0Fjk
– 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
15. Is it a solid or a liquid?
• Exploration:
• 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
help!
• Go ahead and do the exploration now…it will make the
rest of the lecture make more sense – Besides its FUN!!!
16. Properties of Layers
• Crust – solid – conducts heat
• Upper Mantle – solid with liquid
properties – convects heat
• Lower Mantle – solid rock –
conducts heat
• 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
molecule
17. Convection in Asthenosphere
• Heat from core changes
the density of the
material.
• As temp rises density
decreases and fluid rises
• As temp decreases,
density rises and fluid
sinks
• This movement is called
a convection current
which moves the
asthenosphere and thus
the crustal plates
attached to it.
