How Do We Determine The Direction and Speed That Plates Move?
How do we describe the movement of plates?
○ We measure location on Earth using longitude and latitude
○ Latitude is measured as the distance North or South of the equator
○ Longitude is measured as the distance East or West of the prime meridian
West or -
East or +
North or +
(West and South = ( - )
(East and North = ( + )
South or -
○ The directions that a plate is moving (based on longitude and latitude) are combined to determine the azimuth.
■ 0° points to north
■ 90° points east
■ 180° point south
■ 270° points west
○ To measure the azimuth you can measure the angle between the arrow and add/subtract it from one of the angles above.
○ In addition to describing the direction that plates move, we also have to measure how fast they are moving.
○ The speed the plates move is called a rate
■ rate = distance/time
○ The rate of plates is described in mm/yr which is equivalent to km/myr.
One method we use to determine how plates move is to look for hot spots.
○ Shows how plates have moved move over millions of years
○ Hot spots form where narrow plumes of magma rise by connection from the core mantle boundary.
○ The magma continues to rise in the same same spot for millions of years.
○ IF this is true, what would the evidence look like?