TECTONIC PLATES great wines depend upon them


 Tectonic Plates; Wine From Earthquakes

Tectonic Plates plus Geologic forces and fracturing of California over Millennia has created the sublime environment responsible for production of it’s fabulous wines  – Dave Purcell

Pacific Plate Subduction

Pacific Plate Subduction

California is riven by faults that are the result of the Pacific Plate moving part of the state to the north as the American plate stays in place.  As the plate moves north it plows under the North American Plate (See above) and over millions of years changes the landscape, causing bays and ocean to change and pushing up our coastal range of mountains.  A result is that coastal micro-climate weather systems are created throughout the state.



A result of the enormous pressures on the eastern side of the San Andreas Fault below:

Map of California's FaultsImage courtesy of USGS and Google Maps

Map of California’s Faults
Image courtesy of USGS and Google Maps Fault cause numerous surface and deep cracks in the earth that are also faults.  As the plate slowly crash faulting occurs all over twisting, breaking and churning rock and soil, pushing old marine sediments with their limestone fossils inland along the coast creating a rich brew of soils over Millions of years.

























While the slow creep of the boundary fault that travels north/south through the state builds pressure by only a few inches a year, the long time between release of energy through a major earthquake can move mountains several feet higher each time they occur.

So . . . What does this have to with making great wine?


New mountains create climate change by trapping clouds and moisture. As they are pushed up by pressure from the tectonic plates, gravity, moisture, rain, freezes, glacial moraines, and their sheer weight pull rock down and grind it to complex mineral rich sediments and gravel. How does this affect California wines? Grape vines need the right terroir (environment); moisture, prevailing winds, Sun and varied micro-climates do a lot to help, but without the soil conditions provided by tectonic forces California would not have as many high quality wines,

Most of California’s finest wineries are situated along the coastal areas and throughout the hills, valleys and mountains formed by Tectonic Plate action as can be seen in one of the images below color coded to show where different eras deposited rock and soils suitable for growing grapes.

major faults 2-u297

wine districts-u292

California Wine Districts


Geologic Faults in Napa and Sonoma

Geologic Faults in Napa and Sonoma
















Rutherford Bench in Napa Valley

One of the States’ most famous wine making areas was created by the incursion of San Pablo Bay during the ancient geologic changes created by interaction of the two massive Plates colliding as the western plate drove north taking part of the west coast along with it. The Rutherford Bench  was built by the sea depositing sediments as it flooded the area leaving mineral rich soils that grape vines love to grow in. Not many other agricultural products can grow in these soils that produce some of our country’s finest wines.

 Wineries making wines from vineyards in the “Rutherford Bench” include some of the greatest names in the history of Napa Valley: Beaulieu (Georges de Latour Private Reserve), Inglenook, Heitz Martha’s Vineyard,  Freemark Abbey (Cabernet Bosche), Robert Mondavi, and, many others

You cannot see the Rutherford bench, but there are other named benches that are visible from mountains being ground down by geologic forces and the sharply defined alluvial gravel fans made from a stew of minerals that impart special characteristics to wine made from grapes grown on those benches.

An example below is a satellite photo of the Santa Maria Bench north of Santa Barbara, California below, and also a Terrain photo at the same location:  Wineries are located all along this Bench. 

Santa Maria Bench Satellite photo

Santa Maria Bench Satellite photo













Santa Maria BenchTerrain Map

The same map as above as a Terrain Map









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