Magnetic Anomalies

Question 1

Discuss how sea-floor spreading was discovered?

Answer 1

1962- Adm. Harry H. Hess said the sea-floor is not permanent.
It is created at MOR and spreads away, and is recycled at trenches.

Question 2

What causes the alternating polarity of magnetic paleo-inclination

Answer 2

It can’t be that the continents move that fast, or that the rocks flipped after they form.

We know now today that are caused by reversals in earth’s magnetic field.

Question 3

geophysical anomaly

Answer 3

observed value-scientifically predicted value

positive anomaly-more is observed than expected. negative anomaly-less is observed than expected

Question 4

How are magnetic anomalies measured?

Answer 4

Routine measurements: Total strength of the geomagnetic field via magnemeter.
There is unexpected variation in the geomagnetic field on the sea floor.

Question 5

What are the patterns in marine magnetic anomalies?

Answer 5

Alternating bands of positive and negative magnetic anomalies.
Parallel to MOR
Symmetrical with respect to ridge cres (which is always positive)

Question 6

The Vine-Matthew Hypothesis

Answer 6

Sea-floor spreading: new oceanic lithosphere is created at MOR by magmatic processes.

Question 7

What causes offset of stripes in marine magnetic anomalies?

Answer 7

Ridge-Transform-Rdige

Question 8

Possible causes of magnetic quiet zones

Answer 8

very rapid spreading
Not recorded by TRM
change in mechanism of creating ocean floor?
Possible other causes.

Question 9

Magnetic quiet zones with no reversals

Answer 9

true quiet zones