SME
Physical Geology · Problem type
Hotspot tracks
Use this for “A seamount 2,400 km from the active volcano is 30 Ma old. How fast does the plate move?”
Chart
d = 80t
The line goes through (0, 0) and (1, 80).
t = 30 Ma
d = 2,400 km
v = 80 mm/yr
This is an example. Type your own values to start a new problem.
v (mm/yr)
=
d (km)
÷
t (Ma)
Formulas
v
=
d
t
80
=
2,400
30
Assumptions
•
The hotspot stays still in the mantle, and each volcano in the chain formed over it.
•
Distance is measured along the track from the active volcano; age is when the volcano formed.
•
1 km per million years is 1 mm per year, so km ÷ Ma reads straight as mm/yr.
Step-by-step
WE KNOW
d = 2,400 km, t = 30 Ma
FIND
plate speed (v)
Step 1 · Find plate speed (v)
Use v = d ÷ t
The
plate
carried
the
volcano
d
kilometers
off
the
hotspot
in
t
million
years:
distance
over
time.
v
=
2,400
30
v
=
80
mm/yr
Check
Put the numbers back in. Both sides should match.
80
=
2,400
30
✓
Topic check
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