Transcript Mass Wasting

17.2 Notes:
Earth’s Magnetism
Main Points:
All magnets have a north & a south pole.
S
N
Opposite poles attract.
S
S
Like poles repel each other
(ie south repels south, north
repels north).
Types: Permanent magnets & electromagnets
Electromagnet: Can only display magnetism
when there is an electric current source.
They are found in motors, hard drives, and
tons of other devices.
Permanent Magnet:
The magnetic field is generated and maintained by
the internal structure of the material itself.
Earth’s Magnetosphere
Magnetic Field Lines:
Describe:
These allow you to figure out which way a
magnet will align.
Lines exit south pole & enter at north pole.
Magnetic North Pole
Main Points
It’s not the permanent geographic north pole!
It shifts about 10km/year.
Declination
Define
The angle of difference between the geographic (G-N) &
magnetic north (M-N) poles.
20
degrees
M-N
G-N
Pole Reversals
Length of Cycle
The poles REVERSE approx every 250,000 years.
Last reversal was more than twice as long: about 740,000 yrs ago!
If you were alive about 800,000
years ago, and facing what we
call north with a magnetic
compass in your hand, the
needle would point to 'south.'
Ocean floor evidence of Pole Reversals
Location:
Areas where crust is actively being formed at mid-oceanic ridges.
Describe:
Location:
Lava pushes its way up thru seafloor & cools & solidifies.
This reveals the alignment of magnetic minerals w/in the sea floor.
Scientists can see a banding pattern.
Young rocks are nearer the ridge, older
Rocks are further away.
This banding also reveals pole reversals
that have occurred.
Earth’s Liquid
Outer Core
Solid Inner Core:
Composition: IRON & Nickel!
Composition: IRON!
Motion: Constantly
moving in convection cells
around the inner core!
Describe Theory
The liquid outer core swirls around the inner core.
Iron in the outer core acts as a conductor & creates a magnetic field.