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Natural History

GEOLOGY  
Big Basin's landscape reveals the dynamics of the ever-changing California coast. Most (but not all) of the changes are slow enough that even the redwoods don’t notice. Nonetheless, the forces are powerful almost beyond comprehension and are responsible for the landscape we see today.
  
The rocks that make up Big Basin are mostly sedimentary rocks, from the Tertiary time period between the extinction of the dinosaurs about 60 million years ago and the beginning of the Quaternary period about 2 million years ago. These rocks are the debris from older rocks that were eroded and then deposited in the ocean when the area that is now Big Basin was under water. The rocks rest on top of a layer of granite called “basement rocks.” The granite rose, as a hot liquid, toward the surface and cooled underwater about 80 million years ago. This granite is well exposed along Ben Lomond Mountain. 
  
The granite, as well as the sedimentary rock on top, are part of a huge chunk of land known as the Salinian Block, measuring about 50 miles by 300 miles. The block is bounded on the east by the San Andreas Fault and on the west by the Sur-Nacimiento Fault. This block is a chunk of the North American Continental Plate that was torn out of the continent and is being dragged north by the movement of the Pacific Plate. At one time the area that is now Big Basin was about 200 miles south of its present location. The park itself is cut through by the Ben Lomond Fault—related to the San Andreas. The fault runs more or less east-west and is just south of park headquarters near Berry Creek Falls.

During the last 60 million years, the land south of the Ben Lomond Fault has risen 6,000 to 10,000 feet compared to land north of the fault. This uplift is responsible for the creation of Eagle Rock, Mt. McAbee and Pine Mountain. As the land rose, East Waddell Creek continued to cut through the rock on its way to the ocean. Occasionally fault movement would raise the land south of the fault line and dam the creek, creating a lake. The lake would collect sediment on its bottom and eventually the channel would be reopened and the lake would drain. The “Big Basin” that gives the park its name is one of these former lakes. 
  
Big Basin is full of evidence that the park isn’t as serene as it may appear. The Salinian Block continues its slow migration north, and Eagle Rock is still on the rise. Waddell Creek is still cutting its way through the rock while massive slides continue to change the faces of the mountainsides. 
   
TREES and SHRUBS
Ask at the Visitor Center for the "Easy Field Guide for the Big Basin Forest Habitat." 

Coast Redwood
• Can grow to over 370 feet tall
• Can live to be over 2,500 years old
• Has reddish bark
• Has small, round, thumbnail-sized cones that contain about 50–150 small seeds
• Has flat leaf branchlets with a row of needles on the sides
  
Douglas-fir
• Grows over 300 feet tall
• Can live to be about 1,000 years old
• Often mistaken for a redwood
• Has gray, tough, scaly bark
• Has soft needles that grow like bottlebrushes
• Has large cones, with modified scales that look like little mouse tails and feet
   
 Tan Oak
• A short tree that grows in the deep shade of the old-growth redwood forest
• Not a true oak, but closely related
• Its acorns are an important food for many forest creatures
• Look for a “parking lot” pattern on its leaves
  
 Huckleberry
• Common shrub, grows in deep forest shade
• Produces crops of edible, dark-blue berries
• Has glossy, dark-green leaves all year
• Has fragrant and lantern-shaped flowers
  
 BIRDS
  Steller’s Jay
• Blue with a black head, crest, and shoulders
• Loud, raucous, and aggressive
• Has a “chak-chak-chak” call
• Related to crows and ravens
• Will eat any available food. Do not feed them or leave crumbs around.
   
  Acorn Woodpecker
• A medium-size woodpecker with a dark back and white neck, throat and forehead. Males have a red cap.
• Often seen and heard around snags (standing dead trees) where nesting cavities exist
• Can store up to 50,000 acorns in a snag, creating a “granary”
• Listen for drumming and a laughing “waka-waka” call
  
 Dark-eyed Junco
• Small, common bird with a brown body and distinct white stripes on tail feathers
• Male has an intensely dark head and shoulders
• Do not feed!
  
 Common Raven
• Large and jet-black, with a long black beak
• Not native to the redwood forest ecosystem
• Makes a large range of sounds, but most often a guttural “raaach, raaach”
• The diamond shape of its tail in flight distinguishes it from its smaller cousin, the crow
  
 MAMMALS
 Raccoon
• Most active at night and very interested in visitors’ food and trash. Please be crumb clean!
• Has a black mask across its eyes and alternating dark and light rings on its tail
• Has a lumbering walk and leaves prints that look like little hands
   
 Gray Squirrel
• A tree dweller that is active during the day
• Gray with a large bushy tail. Large compared to other squirrels
• Barking cough
• Eats fungi and seeds and stores acorns in the ground for winter food
• Outnumbered by the introduced eastern gray and fox squirrels
  
 Black-tailed Deer
• Browses on small plants, shrubs and acorns
• Males grow antlers in spring and summer and shed them in winter
• Shed antlers are an important source of minerals for smaller mammals in the forest
 
  Merriam’s Chipmunk
• Has a brown, striped body
• Smaller than a squirrel and very fast
• Makes a distinctive “chip” sound emphasized by jerky tail movements
   
CLIMATE CHANGE
In a time of climate change, redwoods are an asset. Their size and longevity help them store more climate-altering carbon dioxide than other plants. Even old redwoods continue to grow, each year adding more carbon-filled wood than smaller, younger trees. After redwoods die, their rot-resistant wood keeps that carbon out of the atmosphere for a long time. 

Could redwoods be harmed by climate change? They do not seem to be suffering so far. But scientists say that increasing temperatures, along with decreasing summer fog, could pose a threat in the decades to come.

Scientists from Save the Redwoods League are actively studying the effects of climate change on the redwoods of Big Basin. Through the League’s Redwoods and Climate Change Initiative, permanent research plots have been established to look at the redwoods and sword ferns. To find out more about the effects of climate change in Big Basin and the other California redwood parks, go to this Save the Redwoods League web page.