This document summarizes a seminar on sea floor spreading presented by Rimita Tikader. It describes how in the 1950s, scientists mapped the mid-ocean ridge using sonar and discovered the ocean floor was not flat, peaking their curiosity. In the 1960s, Harry Hess proposed that hot, less dense material rises at the mid-ocean ridge, flows sideways, and carries the sea floor away from the ridge, creating new sea floor. This process is called sea floor spreading. Supporting evidence includes samples of molten rock and magnetic stripes on the sea floor that support the theory.

1. SEMINAR ON
GEOLOGYTOPIC :- SEA FLOOR
SPREADING...
GUIDEDE BY:-
RIMITA TIKADER
SUBMITTED BY :-
DEVASHISH SAHU
(M.Sc-2nd sem. )

2. content
•WHAT IS SEA FLOOR SPREADING?
•SUPPORTING EVIDENCES.
-Molten material.
-Magnetic stripes.
-Drilling samples.

3. •In the 1950s scientist mapped the mid-ocean ridge
using SONAR.
Sea floor spreading

4. •The scientist found out that the ocean
floor was not flat.
•This discovery peaked their curiosity
to discover what the ridge was.

5. •Early 1960s – HERRY HESS ,together with
ROBERT DIETZ.
•HESS proposed hot , less dense material from
below the earth’s crust rises towards the surface at
the mid-ocean ridge.
•Material flows sideways carrying the sea floor away
from the ridge ,and creates a crack in the crust .

6. •Magma flows out the crack ,cools down and
becomes the NEW SEA FLOOR.
•HESS called this process SEA FLOOR
SPREADING.

7. •MID OCEANIC RIDGE – The longest chain of
mountain in the world these are divergent plate
boundaries.
There are huge mountain ranges called ridges.
Ex- Mid –Atlantic Ridge.

8. SUPPORTING EVIDENCES
1. MOLTEN MATERIALS -
•At the mid –oceanic ridge ,molten material rises up
from the mantle and spreads out,pushing the older
rocks to both sides of the ridge.
•Rocks shaped like pillows show that molten material
has erupted again and again from cracks along the
mid-ocean ridge and cooled quickly.

9. 2. MAGNETIC STRIPES -
•Magnetic surveys conducted near the mid-ocean ridge
showed elongated patterns of normal and reversed
polarity of the ocean floor in bands paralleling the and
symmetrically as mirror image on either side of it.

10. 3. DRILLING SAMPLES -
•The GLOMAR CHALLENGER is a drilling ship that recovered
drilling samples from the ocean .
•They studied the age of the rocks sampled .
•They found that the farther from the ridge ,the older
rock.
•The youngest rocks were at the center of the ridge.

11. THANK YOU
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