1intact volcanic rocks of age 300 Ma are found in continental lava flows at a si
ID: 291914 • Letter: 1
Question
1intact volcanic rocks of age 300 Ma are found in continental lava flows at a site with geographic latitude 55 degree north. the magnetic inclination of the rocks is found to be 15 degree. Assuming an axially aligned paleo-dipole, estimate the amount of northward continental drift implied by the above data
2a detailed plate-tectonic reconstruction gives a Northward continental drift for the site above that differs from Northward motion implied by the geographic latitude and magnetic inclination. Give two possible reasons for this discrepancy.
Explanation / Answer
we know that,
Tan(I) = 2Tan ( ?)
where I is the mgnetic inclination
? is the paleolattitude
thus, Tan 15 /2 =Tan ?
?= 7.632,
therefore the northward continental drift is 55 degree(present latitude) - 7.632 (paleolatitude)
=47.368 degrees.
2. the site above this differs from orthward motion due two possible reason:
a)may be that sight was in a different plate and moved differently.
b)the sight was formed at different geologic time with different magnetic field prevailling that time causing difference in magnetic inclination