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RE: well-lit dinosaurs
Title: RE: well-lit dinosaurs
At 10:42 AM -0500 3/2/01, Thomas R. Holtz, Jr. wrote:
[mailto:firstname.lastname@example.org]On Behalf Of Gavin Rymill
>This is only tenuously a list topic but the BBC
website still managed to make it a dinosaur
>Still interesting though.
Cool stuff. Apparently preliminary data
suggests that the Earth's magnetic field during the Long Cretaceous
Normal (C34n, running from the lower Aptian (c. 120 Ma) to the
beginning of the Campanian (c. 83.5 Ma)) was three times the present
This mid-Cretaceous is an interesting time for a
number of (quite possibly interrelated) reasons:
*Highest sea levels since the Cambrian (at least),
making it the highest in post-Pangaean history
*Higher activities of the mid-ocean
*Faster rates of sea-floor
*Extremely low temperature gradient from
equator-to-pole (that is, climate at the equator and climate at the
poles were very similar, and hot)
*Greater total separation of landmasses than at
present, due to the net effects of plate tectonics and oceanic
*REALLY big South American and African
*Fins, fins, fins, fins...
*Arrival of Asian-style dinosaurs into the Western
Interior of North America (latest Albian/earliest
Yes. And as for the magnetic declination and magnetic field
during the Cretaceous (and other times), then:
I think this depends on where the rocks "were" when
they got magnetized and especially what their "altitude"
was when they got magnetized. If they were down deeper and
"sent" by tectonics to "higher" levels that could
cause a greater B field (closer to the loop currents). If
during a flip period, it might be possible to have local anomalous
high fields. Also if "rocks" are squeezed this would
force the magnetic lines of force to appear closer together (thus
appear like a greater intensity field).
Remember F = qE + (v X B) were B is the magnetic field intensity.
F is the total electic + magnetic force
E is the electric field
q is the charge of the particle
v is the velocity of the charged particle
A compass lines up along a B field direction, since the NORTH
MAGNETIC POLE OF THE BAR MAGNET seeks out the opposite MAGNETIC
POLARITY... the magnetic pole in Northern Canada. North
magnetic pole of the compass is the point, south magnetic pole is the
feathers of the arrow.
B is generated by the loop currents in the molten core... loop
current generates a three D magnetic dipole pattern.
Just my paleodeclination thoughts for the day.
=00= =00= =00= =00=
Marilyn D. Wegweiser, Ph.D.
Adjunct Curator of Vertebrate Paleontology
Cincinnati Natural History Museum
Assistant Professor of Geology
Department of Geology
Ball State University