1. The geomorphology of
California today is the
evidence scientists use
to understand its
geologic history

2. 200mya Oceanic/Continental Subduction
Sediments in the trench build the continent westward
ancient volcanoes
Mt St Helena
East of current CA coast
Magma inland

3. 80mya Magma cools, Intrusive deposits Trench sediments uplifted
Coast range
Sierra Nevada granite
80mya
Subduction ceases
East of current CA coast

4. Coast Range and inland volcanoes create an inland sea
80mya

5. Creates blocks, which uplift and subside
30mya plate fractures
Creates blocks, which uplift and subside
Basin & Range topography
Basin and Range of Nevada

6. Uplifting + weathering expose the granite of the Sierra Nevada
30mya

7. 30mya
The North American
and Pacific plates form
a transform boundary -
The San Andreas Fault

8. Heading NW past Santa Cruz
North through the Carrizzo Plain (central coast)
Heading NW past Santa Cruz
Sharp turn W at Mussel Rock
Gulf of CA

9. Inland sea yields the thick & fertile
soils of the Central Valley
30mya

10. Subduction of the Juan de Fuca plate creates volcanic Cascade range
Mt Shasta
30mya
Subduction of the Juan de Fuca plate creates volcanic Cascade range

12. Earthquakes occur below Earth’s surface, sending waves in all directions

13. primary (p)
secondary (s)

14. A seismometer (seismograph)
generates a
…seismogram
a record of the motion of a free-swinging pen

15. Waves travel at different speeds
The difference in arrival time
increases
with distance from source
Waves have different energies
Wave amplitude reflects ‘quake magnitude
primary
(P)
surface
secondary
(S)

16. The difference
in arrival time of P
and S waves is used
to determine distance from the epicenter
Data from three
stations is used to
pinpoint the epicenter

17. Measuring earthquake magnitude factors in both speed and amplitude
Richter Scale
A base 10 log scale – each greater value is 10 times the previous value