Geology 104 - Spring 2007
Lecture #21

Pinnacles NM, Point Reyes NS, Olympic NP

Pacific Mountain System Physiographic Division - Pacific Border Province

• Includes entire west coast of US
• Lowlands along eastern side, mountain ranges to the west
• Mountains formed through plate tectonics
• Tectonic processes still active throughout province
  

Pinnacles NM

Location and History

• NM 1908
• Small preserve

Geology

1. Stratigraphy: Cenozoic volcanics

• Tertiary
• Mostly tuffs
• Some lava flows

2. Pinnacles

• Weak rock with many cracks
• Some columnar jointing in flows

Plate tectonics

• Located along the San Andreas Fault (SAF)
• Pinnacles is on Pacific side of SAF
• Rocks are related to Neenach volcanics on North America side of SAF

Point Reyes NS

Location and history

• NP 1962
• About 40 miles NW of San Francisco
• Explored by Sir Frances Drake in 1579
• Near site of 1906 San Francisco earthquake epicenter
• Westernmost location in continental US

Geology

1. Stratigraphy

Rock	Age
Sedimentary rock	Tertiary
Granite	Cretaceous
Sedimentary	Triassic

2. Rate of movement

• Averages
  • PR: 590 km in 40 my
  • Pin: 315 km in 23.5 my

• Instantaneous
  • PR: 1906 EQ - 21 feet of movement in minutes

Olympic NP

Location and History

• NP 1938
• On the Olympic Peninsula, across Puget Sound from Seattle
• A place of contrasts
  

Sections of the park

1. High mountains

• Mount Olympus
• Active glaciers
• Features of glacieal erosion & deposition

2. Rain forest

• Highest precipitation in USA
• Led to formation of glaciers
• East side much drier

3. Coast

• Beaches
• Erosional landforms
  • Sea cliffs
  • Terraces
  • Notches
  • Sea stacks

Geology

1. Very complex geology

Formation	Rock	Age
Hoh	Graywacke (dirty ss)	Tertiary
Crescent	Basalt (pillow basalt)	Tertiary

2. Rocks were accreted to North America Plate:

• Convergence of Juan de Fuca and NA plates results in subduction.
• Sediments & basalts were squashed, deformed and thrust up onto continent.

Pinnacles slides

Point Reyes slides

Olympic slides

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