WineGeo: Escarpment and Bench

Just yesterday, following a lovely trip to Toronto and the Ontario Wine Country, I was doing a bit of research in order to write up a blog post about the four sub-appellations of the Niagara-on-the-Lake VQA.  For the record, they are:  Niagara River, Niagara Lakeshore, Four Mile Creek and St. David’s Bench. According to the website for the Wineries of Niagara-on-the-Lake, these four areas are differentiated by soil types, weather, elevation and proximity to “three unique geographical features: the Niagara Escarpment, Lake Ontario and the Niagara River.”

I have to stop right there and promise to write the blog post on the sub-appellations (they are quite lovely) at a later date, because I just realized that in that one short paragraph I spouted off two words that I have no earthly idea how to really define.  And you, dear wine student, if you honest with yourself, must admit that you have done the same thing; you use the words all the time (chatting about wine is so-much-fun) but can you tell me, in your own words, just what exactly is an “escarpment” and what, geologically speaking, is a “bench?” 

Well, neither could I. So, I did some early morning research and am going to try to define those geological terms in simple, regular person’s language, with just a teeny bit of wine geek thrown in.

Escarpment:  An escarpment is basically an area of the Earth where the elevation changes suddenly. An escarpment is often found along the ocean shore, such as the Devil’s Slide area of California Highway 1.  An escarpment can also refer to an area on dry land that separates two level land surfaces, such as Africa’s Great Rift Valley and the Niagara Escarpment (only a small portion of which hosts the famous falls.)

A tiny piece of the Niagara Escarpment

An escarpment usually indicates two different types of land, such as the area of a beach where tall cliffs surround a lower area of sand.  Escarpments between two areas of level land are usually composed of different types of rock or rocks from different geologic eras, one of which erodes much faster than the other. Escarpments can also be formed by seismic action; such as when a fault displaces the ground surface so that one side is higher than the other (scary).

Significant Wine-Related Escarpments include the Niagara Escarpment, the Côte d’Or, the Balcones Fault in Central Texas, and the Darling Scarp in Western Australia. The term “scarp” technically refers to just the the cliff-face of an escarpment, but the two terms are generally interchangable.

Bench: Admit it, you’ve talked in hushed tones about the amazing flavor of Cabernet Sauvignon from the Rutherford Bench….but do you know what is meant, geologically, by the term bench?  Neither did I.  Tchnically, a bench or a “benchland” is a long, narrow strip of relatively level land that is bounded by distinctly steeper slopes above and below it. Benches can be formed by many different geological processes, such as a river (as in a river’s flood plain, or an “abandoned” river bed), waves (if alongside an ocean), or the varying levels of erosion of different types of rock.

Cross Section of Different Types of “Benches”

Thanks to Wikimedia Commons for the diagram of “Bench Structure.” The diagram shows the different ways benches can form, such as structural benches formed by the  erosion of shale beds overlying limestone beds and the more common “river terraces.”

The famous “Rutherford Bench” is a stretch of the Napa Valley, about three miles long, starting in Oakville and heading north to Rutherford.  The bench sits in the middle of the valley floor, surrounded on two sides by small hills. The famous soil of the Rutherford Bench consists of gravel, loam, and sand, much of which was deposited there by earlier advances and retreats of San Pablo Bay.

The term “bench” appears in the discussion of wine regions (though not necessarily AVAs or appellations) frequently:  the Rutherford Bench and the Oakville Bench were both at one time or another considered for AVAs of their own, but to date have not been designated as such. There are however, five “official” wine regions that I could find that use the term:  Kelsey Bench-Lake County AVA, and four VQAs in Ontario: Short Hills Bench, St. David’s Bench, Beamsville Bench, and Twenty-Mile Bench.

References/for more information:

• The Wineries of Niagara-on-the-Lake:  http://wineriesofniagaraonthelake.com/
• National Geographic – Geology: http://education.nationalgeographic.com/education/encyclopedia/
• Bench Image by Cristellaria, via Wikimedia Commons