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Downloads (PDF files)
- 2001 course handout (4 pages)
- PDF table of magma types
(same as table on page 4 of handout)
- PDF table of largest volcanic
eruptions
- PDF table showing the recurrence time
of eruptions
- PDF table of basic volcanic features
- PDF geological map of S.D. county
- glossary for this lecture (PDF)
| Intrusive Structures | Extrusive Structures |
| Mt. Woodson, SD county | a shield volcano in Iceland |
| the batholith in Yosemite | a composite volcano in New Zealand |
download high-res pdf
The Peninsular Ranges are dominated by intrusive rocks (e.g.
Mt. Woodson,
Iron Mt.,
Hot Springs Mt.)
pushed to
the surface during the ~ 70 Mio years of the Cretaceous. These
replaced the older sediments that got eroded away. Only few patches
of these sediments exist in the NE corner of the county in the
mountains. Older volcanic rocks, that are related to andesitic
subduction volcanism, can be found at the western edge
of the batholith.| Ordovician | 500 Mio yr | oldest sedimentary rocks; submarine environment |
| Triassic | 200 Mio yr | Pangea breaks apart; sediments get exposed and eroded; S.D. area somewhere south of equator |
| Jurassic | 190-136 Mio yr | subduction of the Farallon Plate (now gone); andesitic volcanism in Peninsular Ranges |
| Cretaceous | 136-65 Mio yr | intrusion of batholith and uplift of Peninsular Ranges, creating metamorphic rocks (e.g. Julian Schist); andesitic volcanic rocks eroded as well as sedimentary rocks that are replaced by batholith |
| Tertiary(Miocene) | 17 Mio yr | volcanism related to opening of Gulf of California; Baja now on Pacific Plate and moving north relative to North America |