introduction to continental drift

1. Introduction to plate tectonics
Nipin K P
kp.nipin@gmail.com

3. Continental Drift
• Alfred Wegener in 1915
• Super continent – Pangea
• Single Ocean – Panthalassa
• Break up to form – Gondwana land and Laurasia
• Gondwana land: Africa, South America, Australia, Antarctica and India.
• Laurasia: North America, Greenland and Eurasia.
200 Million years ago

5. Plate Tectonics
• W.J Morgan and J Tuzo Wilson – 1967
• Lithospheric plates : 100 – 150 km thick
• Plates can be oceanic + continental
• Size and velocity varies
• Separated by ridges, faults, fold mountain belts and trenches.
Seafloor spreading
Linear Magnetic Anomaly

6. Major Plates
• North American plate
• South American plate
• Pacific plate
• Eurasian plate
• African plate
• Indo-Australian plate
• Antarctic plate

8. Plate Boundaries
• Zone of seismicity, volcanicity and tectonic activity.
• It is a zone of motion b/w two plates – Plate boundary
• Marginal part of a single plate – Plate margin
• Based on relative motion: (i) Divergent plate boundary
(ii) Convergent plate boundary
(iii) Transform plate boundary

9. (i) Divergent boundary (Constructive boundary)
• New crust is continuously created (eg.: Sea floor spreading).
• Plates moves away from each other.
• Shallow focus earthquakes, basaltic igneous activity.
• Eg: Mid Atlantic Ridge

10. (ii) Convergent boundary (Destructive boundary)
• Two plates move towards each other.
• Oceanic-oceanic: Subduction zones: Island arcs
• Oceanic-continental: volcanic arcs
• Continental-continental: Fold mountain belts
• Deep focus earthquakes.
• Eg: Himalayan mountain

11. (ii) Transform fault boundary (Conservative boundary)
• Two plates slide past each other.
• No production or destruction of lithosphere.
• Shallow focus earthquakes.
• Eg: San Andreas fault, USA