Drunk on Petrology - Bedrock Old Vine Zinfandel

 

The next Drunk on Geology is for Bedrock Old Vine Zinfandel by the Bedrock Wine Company. 

Although I am pretty certain that the owners of the winery chose to use the term "bedrock", with the less geological definition of the word as the foundation of their winery, that is not the way a geologist would see it. And I see it, as a geologist would see it. Bedrock Wine Company also has a large number of vineyards, however only one bear's the name "Bedrock" so we are going to focus on that one.

Bedrock definition (courtesy of the Dictionary of Geological Terms 3rd Ed.):

The solid rock that underlies gravel, soil, or other superficial material.

The problem with determining the bedrock of a region, especially an area within a river valley, such as where the Bedrock Vineyards are located, is that the overlying gravel, soil, and other superficial materials are frequently what is published on geological maps. And that is the case here, so we need to infer what indeed is the bedrock beneath the superficial materials. There are sometimes geologic bedrock maps made which interpret what would be the bedrock below the superficial deposits, however I couldn't find one for this region. This map is also a fairly recent map (2017), so I am fairly confident that we can use it to determine the likely bedrock below the sediment. 

Geological Map of the Bedrock Vineyards locality. Map courtesy of the NGMDB. 

The red circle on the map above denotes the area of the Bedrock vineyards. As you can see there is a lot of geologic deposits where the only capital letter is a "Q". The "Q" stands for the Quaternary, the time period they were deposited during and these are the superficial deposits as mentioned above. The Quaternary represents the last ~2.5 million years in the Earth's geological history and runs up to today. These are mostly sediment deposited by the Sonoma Creek that runs down the middle of the valley. 

In order to determine the bedrock from a map like this we need to first look at the bedrock along the outside edges of the stream valley deposits. These are going to be the sediments that begin with capitol letters besides just "Q". You can determine what all of these abbreviations by looking at the original map and legend HERE.

Text from the back of the bottle:

"From vines averaging over 80 years in age planted throughout the diverse state of California, this wine aims to reflect the perfume, freshness, and spice that makes Zinfandel so utterly delicious. Fermented with native yeasts and minimally racked, this wine should provide great short-term drinking but will age gracefully for 5-10 years."

The most notable rock formations are QPge, PMpu, Msvrah, and Msvas. Since QPge spans both sides of the river sediments, I am inclined to believe that this is the most likely bedrock directly below the winery. Even though I said that the deposits starting with a "Q" represented overlying sediment, there is also a capitol "P" on these. The "P" indicates that the unit spans more than just the Quaternary. 

The QPge represents the Glen Ellen Formation. The Glen Ellen Formation is a unit comprised of a mixture of tuffaceous clay, mud, bouldery to pebbly gravel, and sand and silt deposits with interbedded conglomerates. These sediments were deposited in a variety of nonmarine environments, including coalescing alluvial fans, fan deltas, streams, and lakes (per Sweetkind et al., 2010). The Glen Ellen formation is Pliocene to Pleistocene in age and is identified as younger than 3.2 million years old. These rocks were likely deposited in a prehistoric version of the Sonoma Creek in which is currently found in the valley now. 

The PMpu is the Pliocene-Miocene age Upper Petaluma Formation. The Petaluma Formation is dominated by deposits of moderately to weakly consolidated silty to clayey mudstone, with local beds and lenses of poorly sorted sandstone. The environment in which these rocks were deposited consists of transitional marine and nonmarine sediments that were deposited in estuarine, lacustrine, and fluvial depositional settings (per Sweetkind et al., 2010). These rocks represent a much higher sea level than the Glen Ellen Formation, with a mixture of marine and nonmarine rocks deposited within the valley. 

Msvrah (?Rhyolite of Adobe Canyon) and Msvas (Andesite of Shocken Hill) are both a part of the Sonoma Volcanics. The Sonoma Volcanics were deposited across a long range of time from the Miocene through the Pliocene and are described by the USGS as:

"... a thick and highly variable series of continental volcanic rocks, including andesite, basalt, and minor rhyolite flows and interbedded coarse- to fine-grained pyroclastic tuff and breccia, redeposited tuff and pumice, and diatomaceous mud, silt, and sand."

So overall, it is likely the bedrock for the Bedrock Vineyard is the Glen Ellen Formation, however the Upper Petaluma Formation is also likely. These are likely sprinkled with local volcanic deposits from the Sonoma Volcanics as well. 

References
https://ngmdb.usgs.gov/mapview/?center=-122.503,38.3&zoom=14
https://ngmdb.usgs.gov/Prodesc/proddesc_105819.htm
https://pubs.geoscienceworld.org/gsa/geosphere/article/6/3/237/132359

https://pubs.usgs.gov/wsp/1495/report.pdf

Drunk on Petrology - Chalk Hill Syrah

 

The next Drunk on Geology is for Chalk Hill Syrah from the Chalk Hill Estate Winery. 

The name of the Chalk Hill Estate Winery comes from Chalk Hill upon which it sits, but the winery encompasses a rather large area with several different types of soil and bedrock. From their own website:

"In amazing proximity, the soils range from shallow to deep, from thin to thick, from gravel and rock to heavy clay. An old river bed caps one hill; an unusual serpentine vein ranges through another and, under the topsoil, is a distinctive layer of chalk-colored volcanic ash which inspired the name of Chalk Hill, the appellation, and the estate."

Their description of the winery is geologically fantastic, so lets take a closer look at the actual geologic map of the region. 

 

The winery is located within the red circle on the geologic map above. This region, and the surrounding area, is a mishmash of geology. Starting with the purple unit that crosses the middle of the red circle, we have the serpentine vein that is mentioned in the description.  

Geologic Map of the Chalk Hill Winery region. Map located using the NGMDB. 

Although identified by the winery as "unusual", the serpentine band is actually part of a Middle Jurassic formation known as an ophiolite, of which ophiolites are fairly common across California. This is because of how California formed. The diagram below illustrates the subduction zone that was formerly off the western coast of California. 

Diagram of the subduction zone that was formerly off the western California coast. Image courtesy of the NPS. 

The crust of the Earth is made up of plates that move around and a subduction zone is when one plate goes beneath the another plate. When that occurs, a lot of things happen. As the plate descends, it starts to melt. That melted rock then rises back up producing volcanoes, in this instance it is how the Sierra Nevada mountains formed. But as that plate is descending, the overriding plate (in this instance North America) is scraping the top layer of the down-going plate (the Farallon Plate). The scraped material includes any islands in the ocean, other land masses, and even pieces of oceanic crust. This material is known collectively as "accreted terrane", and is how a vast portion of California was built up over time.  

Looking at the pieces of the oceanic crust in particular, as the oceanic crust is formed, it is created at the Mid Ocean Ridge (as seen on the diagram above), by a series of continuous volcanic eruptions. These volcanic eruptions produce layers of different rocks and minerals depending on how the eruption interacts with the other rocks and water in the area. This eventually creates a layer-cake of rocks that are known as an Ophiolite Sequence.

Idealized ophiolite sequence. Image courtesy of Arenas et al., 2007.

One of the lowermost levels of an ophiolite sequence is the Serpentinite layer. The serpentinite is formed from the hydrothermal (hot water) metamorphism of mantle rocks, producing these green mineral rich rocks (most frequently comprised of antigorite, lizardite, and chrysotile) with a surface that looks similar to snake skin (hence the name). 

One of the other main rock formations in the region of the winery is the KJgvs, which is part of the Jurassic-Cretaceous Great Valley complex. This particular series of rocks consists of interbedded sandstone, siltstone, and shale formed within the Great Valley forearc basin as seen in the subduction zone diagram above. These are non-marine rocks including river complexes across the valley. 

Most of the rocks within this region, however, are part of the Sonoma Volcanics,  including the Tsb rock, which is a basalt. According to the USGS:

The Sonoma volcanics constitute a thick and highly variable series of continental volcanic rocks, including andesite, basalt, and minor rhyolite flows and interbedded coarse- to fine-grained pyroclastic tuff and breccia, redeposited tuff and pumice, and diatomaceous mud, silt, and sand. A prominent body of rhyolite flows and tuff with some obsidian and perlitic glass called the St. Helena rhyolite member, occurs in the upper part.

The final location we will talk about would the the eponymous Chalk Hill. Chalk Hill is to the east of the winery with the winery sitting near its base along the Chalk Hill road (as near as I can tell). And as the Chalk Hill Winery website describes, Chalk Hill is indeed not made up of chalk. Chalk is a well known sedimentary rock, most famously found as the White Cliffs of Dover. Chalk itself is made up of tiny fossils of animals called coccolithophores. The microscopic animals form a ball covered in little calcium carbonate plates called coccoliths. When the animal dies, the plates come apart and if enough of the animals are present in the environment, they can accumulated over time to form the rock known as chalk, which is a white to grey colored chalky rock.

However, that is not what we have here. We have a rock that resembles the color and texture of chalk, but is not actual chalk. This rock is made up of ash and other pyroclastic deposits from the nearby volcanic zones produced from the subduction zone that continued off to the west. Ash, also a white to grey chalky rock, has a strong resemblance to chalk, hence the name of the region and the hill. When ash falls, it quickly hardens and produces a rock layer known as tuff. Although the term tuff can refer to any pyroclastic (volcano produced) rocks. The tuff of Chalk Hill was deposited mostly within water bodies in the region as part of the Sonoma Volcanics. These ash deposits have been dated to ~4 to 5 million years ago. 

References
Arenas, Ricardo & Catalán, J.R. & Martínez, Sonia & García, Florentino & Abati, Jacobo & Fernández-Suárez, J. & Andonaegui, P. & Gómez Barreiro, Juan. (2007). Paleozoic ophiolites in the Variscan suture of Galicia (northwest Spain): Distribution, characteristics and meaning. 10.1130/2007.1200(22). 
https://pubs.usgs.gov/wsp/1495/report.pdf
https://www.nps.gov/subjects/geology/plate-tectonics-subduction-zones.htm

https://ngmdb.usgs.gov/Prodesc/proddesc_52762.htm

https://pubs.geoscienceworld.org/gsa/geosphere/article/8/2/342/132533/Evolution-of-the-Rodgers-Creek-Maacama-right

Drunk on Petrology - Soda Rock's Lord Snort Blanc

 

My next Drunk on Geology post is for Soda Rock's Lord Snort Blanc from the Soda Rock Winery. 

The winery was named "Soda Rock" back in in the 1930's following the repeal of prohibition, a name that has been passed down through several different owners. The original name of the winery descended from the Soda Rock Post Office and General Store, a building which the winery took over after it had fallen into disrepair. The name of Soda Rock appears to be named after an outcrop of rock along the nearby Russian River, identified on topographic maps simply as "Soda Rock". 

Soda Rock feature on the topo maps. Image from the NGNDB.

Since the actual Soda Rock lies within the Russian River it is a bit difficult to identify which specific geologic formation it belongs to. However we can look at the nearby geological formations and see what fits best. The closest, and most likely, is the Pleistocene and Pliocene age (~5-2 million years old) Glen Ellen Formation (QTge on the map below). The Glen Ellen Formation is identified as "compact lenticular poorly sorted silly clay, sand, poorly cemented conglomerate, and local fairly loose sand and gravel. There is also a tuffaceous member of the Glen Ellen Formation within the region, although not mapped right in this area.

Soda Rock feature on the geological maps. Image from the NGNDB.

The other potential rock near that area are the slightly more pinkish rocks on the map above. These are Pliocene and Miocene age (~20-5 million years old) Sonoma Volcanics (Tsb on the geologic map). Which are mainly andesite and basalt lava flows, pyroclastic rocks, and mud flows with interbedded volcanic sediments. Thick sections of poorly permeable tuff breccia and rubbly and fractured zones in lava yield water to wells. 

Soda Rock from Google Street View. 

Based on the view from Google Earth, which luckily had a "street view" along the Russian River, we can get a fairly good view of the Soda Rock itself. Unfortunately, this is no substitute for going out and viewing the rock in person. So any guess as to what the rock actually is, is entirely a guess on my part, but this looks to me more like a volcanic deposit. This means that the Soda Rock itself is more likely to be part of the Sonoma Volcanics, than a sedimentary deposit, which would be part of the Glen Ellen Formation.

The term "soda" is also a geological term, although one that is not often used in scientific circles (from what I am familiar with). It seems to be a more commercial/industrial term and it refers to sodium, specifically sodium carbonate (Na2CO3). Sodium within rocks also has a tendency to produce a grey, ashy looking rock, of which the term "soda ash" is also another commercial term for the word "soda". So, regardless of geology, the Soda Rock in the river, does appear to have a grey, ashy look to it, hence rendering it understandable that one would call it "soda". 

Text from the bottle:

"Located in the heart of the renowned Alexander Valley in Northern Sonoma County, Soda Rock Winery's rich heritage dates back to 1869 when the winery site housed the Soda Rock Post Office and General Store.

Today Soda Rock Winery's Village Heritage continues as owners Ken and Diane Wilson bring new life to this historic site with the best that Alexander Valley has to offer."

As a side note, I picked the Lord Snort Blanc as the wine for this post because the whole reason we stopped at this winery was the fantastic pig sculpture just outside the main wine tasting building, dubbed Lord Snort. A sculpture by artist Bryan Tedrick that is 20,000 pounds steel statue measuring 32 ft wide, and 20 ft tall. Lord Snort made his debut at the Burning Man Festival and eventually found his way to the winery.

 

And of course we had to take our picture in front of Lord Snort with our Lod Snort Blanc. 

Drunk on Seismology - Ram's Gate Vineyard

My next Drunk on Geology post is for the Ram's Gate Vineyard itself. When touring the vineyard I noticed a little sign denoting the "Faultline Vineyard", and while the winery doesn't have a geological themed name or label, I thought this would be a fun addition.

Upon further inspection it appears that the entire winery is located along the southernmost extent of the Rogers Creek Fault. The Rogers Creek Fault is the northern extension of the much better known Hayward Fault, one of the most active faults in California. The two faults connect beneath San Pablo Bay and it was unknown until recently if they were physically connected or just ran parallel to each other. The size of a potential earthquake is directly tied to the size of the fault. The larger the fault, the larger the potential earthquake. And with these two major faults being identified as two parts of the same fault, that increases the size of the potential earthquake along the Hayward-Rogers Fault Zone significantly (from a ~6.7 to a ~7.4). 

Fault map of the Ram's Gate Vineyard showing the Rogers Creek Fault Zone.

A 2018 study of the fault provided a recent, in-depth review of the fault with updated fault maps from San Pablo Bay up through Healdsburg, part of the Sonoma Valley winery region. In the map above you can see the fault trace running right through the center of the Faultline Vineyard, which is located to the east of the main tasting room building. 

Here is a shot towards the west, facing the main tasting room building along the main path of the Faultline Vineyard. In this photo the fault trace above is located to the right of the photo. The Rogers Creek Fault is an active fault with the most recent earthquake likely occurring sometime during the mid 1700's and has a recurrence interval between 131 and 370 years.

Here is a photo looking across the fault towards the north, which would be located approximately midway down the middle of the photo running from left to right across the vineyards. 

References
https://pubs.usgs.gov/sim/3410/sim3410_mapsheet.pdf
https://www.researchgate.net/publication/228751159_The_most_recent_large_earthquake_on_the_Rodgers_Creek_fault_San_Francisco_Bay_area

https://advances.sciencemag.org/content/2/10/e1601441

Drunk on Paleontology - Cambria Benchbreak Chardonnay

 

The next Drunk on Paleontology post is for Cambria Benchbreak Chardonnay from the Cambria Estate Vineyards and Winery in Santa Barbara, CA. 

The name of the winery, Cambria, comes from the geologic time unit, the Cambrian, which lasted from 541 to ~485.4 million years ago. The Cambrian is the first geologic Period within the Era known as the Paleozoic, which also happens to be the first Period within the Phanerozoic Eon (which followed the Precambrian). 

The Geological Society of America's geological time scale. Available here for download in PDF.

Geological time periods are named after people, places, or some aspect to the Earth from which the rocks are found that date to those time periods. The Cambrian and all of the time periods around it are no exception.

The Cambrian was named after Cambria, which is the Roman name for Whales. This is where rocks of this age were first studied by Adam Sedgwick.

The Paleozoic, of which the Cambrian is the first Period within, means "Ancient Life" (paleo = ancient, zoic = life).

And the Phanerozoic, of which the Paleozoic is the first Era within, means "Visible Life" (phaner = visible). 

The Cambrian is a remarkable period within the Earth's history. So much so, that everything before the Cambrian is simply identified as the Precambrian. It was initially thought that the Cambrian represented when life first appeared on Earth, hence it starting off the Visible Life (Phanerozoic) eon. Scientists now know that is not the case, having found fossils and other evidence of life from rocks that are far older than the Cambrian. 

The Geological Time Scale in general was developed by the fossil record. When major animals appeared and disappeared are the basis for the divisions that we now know. Major extinction events mark major boundaries within the time scale such as the Permian Extinction, where 95% of all life on Earth went extinct and marked the end of the Paleozoic, and the Cretaceous extinction, where 80% of all life on Earth went extinct and marked the end of the Mesozoic. 

Treptichnus pedum from the Lower Cambrian. Image courtesy of Buatois, 2017.

The start of the Cambrian, and for that matter the start of the Paleozoic and Phanerozoic (since it is all the same start) is marked by the first appearance of "complex" life. To mark this notable occurrence one particular species needed to be identified. And for this a trace fossil was actually used. Trace fossils are not actual body fossils of animals but marks left behind by the animal, such as footprints, or burrows. And although trace fossils are difficult to ascribe to a particular species, they can generally ascribed to a group of animals based on morphology of the trace left behind. Trace fossils are also given names like body fossils, broken down into ichnogenus and ichnospecies (ichno = trace). For the Cambrian, the trace fossil chosen as the boundary designator is Treptichnus pedum.  

The Cambrian is most well known for the event dubbed the "Cambrian Explosion", which was originally meant to represent the sudden appearance of life on Earth and the quick evolution of new life forms. However, as more fossils are discovered from rock units older than the Cambrian, this moniker has become somewhat incorrect. Although now the Cambrian Explosion has taken on a new meaning. It now represents the explosion of animals with more readily preservable body parts, like shells and skeletons, because without which the fossils are more difficult to discover.

Text from the back of the bottle:

"Our cool coastal vineyard consists of ancient fossilized seashells, shale, limestone and sand. The fog-swept vines have endured since the 1970s. This unique estate sits 400-800 feet above sea level on a bench that overlooks Santa Maria Valley before plunging down to the Sisquoc River. We invite you to experience the results of sustainable farming and artisanal winemaking from our vineyard to your glass. Enjoy."

Upon looking at the location of the winery, the winery itself covers a lot of land within the Santa Maria Valley, which sits upon mostly river alluvium along the valley floor (anything that starts with a "Q" on the map below). However, the wine property also covers some land directly upslope of the valley into the mountains. Here the rocks aren't Cambrian though, they are actually Miocene in age (~17 to 5 million years old). Much, much younger than the Cambrian. 

Geologic Map section where the Cambria Winery is located. Full map with Legend is located at the National Geologic Map Database.

These rocks are part of the Monterey Shale deposit which is a marine, mostly biogenic shale made up of three units, two of which are within the Cambria property boundaries. The lower unit (Tml on the map above) has cream-white weathering, is a thin-bedded fissile semi-siliceous shale, with thin tan dolomitic layers, and a few thin fine-grained sandstone units. The upper layer (Tm on the map above) is similar but doesn't have dolomitic or sandstone layers. 

So, although the winery doesn't sit on Cambrian rocks, it does take its name from one of the the most important time periods in geological and paleontological history, which is a pretty good name to base anything off of.

References

https://www.cambriawines.com/

Buatois, Luis. (2017). Treptichnus pedum and the Ediacaran-Cambrian boundary: Significance and caveats. Geological Magazine. 155. 1-7. 10.1017/S0016756817000656

https://ngmdb.usgs.gov/ngm-bin/pdp/zui_viewer.pl?id=34280

Drunk on Astronomy - Shooting Star Pinot Noir

The next Drunk on Geology post is for Shooting Star Pinot Noir from the VML Winery in Healdsburg, CA. 

VML Winery has these absolutely gorgeous labels for some of their wines which denote different cosmological features such as "Sun", "Earth", and here "Shooting Star". For those who don't know, a shooting star is not actually a star at all, but occurs when a bit of rock or other debris enters into the Earth's atmosphere, creating a streak of heated air upon entry. These pieces of rock or other debris can either completely burn up, or only partially burn up, with the remaining portion of the debris coming into contact with the Earth. 

Scientists have several different names for the rocks that travel through our solar system depending on how they interact with the Earth and it's atmosphere. The most general is a meteoroid, which are chunks of rock that are floating in space that are smaller than a kilometer in diameter. A meteor is what would be the scientific term for a "shooting star". These are the flash of light that you see when a meteoroid enters the atmosphere. It is good to note that the meteor specifically refers to the flash of light itself, not the actual object, which is still referred to as a meteoroid. Once that bit of debris reaches the surface of the Earth, it is then identified as a meteorite. 

Two other major objects that travel through the solar system are comets and asteroids. Comets are bodies of ice, rock, and organic compounds that can be up to several miles in diameter that are thought to originate beyond the orbits of the outermost planets. Asteroids are large, rocky bodies (greater than a kilometer in diameter) in orbit around the sun. Asteroids can be composed of rock or metal, like nickel and iron, and most are thought to have formed from the incomplete formation of a rocky planet between Mars and Jupiter, now known as the Asteroid Belt. 

During various times of year there are events known as "meteor showers", this is when there are numerous shooting stars across the sky generally within a short period of time. Although named for the constellation in the sky at the time of the events, these meteor showers are a result of debris shed off from the tails of comets or asteroids as they orbit through the solar system. These are the major meteor showers during the year and when they occur:

Quadrantids        December/January

Lyrids                  April

Perseids               August

Orionids              October

Leonids               November

Geminids            December

The path of Earth crosses various comet's orbits throughout the year creating fields of debris through which the Earth then travels. Image courtesy of NASA. 

The Quadrantids Meteor Shower is produced by the orbit of asteroid 2003 EH1. Asteroid 2003 EH1 takes 5.52 years to orbit the sun once. It is possible that 2003 EH is a "dead comet" or a new kind of object being discussed by astronomers called a "rock comet."

The Lyrids Meteor Shower is produced by the orbit of C/1861 G1 Thatcher, which was discovered on 5 April 1861 by A. E. Thatcher.

The Perseids Meteor Shower is produced by the orbit of comet 109P/Swift-Tuttle, which takes 133 years to orbit the sun. 

The Orionids Meteor Shower is produced by the orbit of comet 1P/Halley (i.e. Halley's Comet), which takes 76 years to orbit the sun and was named after Edmund Halley who accurately predicted the orbit time and when the comet would next arrive. 

The Leonids Meteor Shower is produced by the orbit of comet 55P/Tempel-Tuttle, which takes 33 years to orbit the sun.

The Geminids Meteor Shower is produced by the orbit of  asteroid 3200 Phaethon, which takes 1.4 years to orbit the sun. Phaethon is also considered to be possibly a "dead comet" or a "rock comet."

References

https://spaceplace.nasa.gov/meteor-shower/en/

https://hubblesite.org/quick-facts/science-quick-facts

https://solarsystem.nasa.gov/asteroids-comets-and-meteors/meteors-and-meteorites

Drunk on Volcanology - Scoria Chardonnay

 

The next Drunk on Geology post is for the Scoria Chardonnay from the Scoria Vineyards and Winery. 

The Scoria Vineyards and Winery are located in the same region as the previous Drunk on Geology post, Cinder Wines, the Snake River Plain, and both even have geologically related names. The words "cinder" and "scoria" are often used interchangeably within the geological nomenclature. 

Scoria is a volcanic rock that solidifies as basaltic lava is splattered out of a volcanic vent. Lava is categorized by its chemical composition, which also effects other aspects of it. Basaltic magma is a low silica (quartz) magma, meaning it tends to have a low viscosity (runny), is darker in color (black), it has a high iron and magnesium content (rusts), and it is also generally hotter when it erupts. 

Sample of scoria from Utah's Ice Spings Volcano. 

When you get a specific type of volcanic eruption where the basaltic lava splatters out, the lave then cools in the air with lots of air holes in it. This gives the lava rock a holey, lightweight appearance, like pumice, but black in color (as seen in the picture above). Over time these scoria rocks pile up around the vent eventually creating what is known as a cinder cone volcano. Cinder, again, referring to the scoria rocks.  

Text from the back of the bottle:

"Scoria's chardonnay takes on subtle tropical fruit flavors with expansive finishes of vanilla and French oak.

Our vines root deep into soil laced with dark volcanic scoria rock."

Pathway of the Yellowstone Hotspot across Idaho. Image courtesy of the Digital Geology of Idaho.

Generally, the Scoria Vineyards and Winery are located within the Snake River Plain. This is a region where the Yellowstone Hotspot once passed through. In actuality, the hotspot didn't move but the North American plate passed over the hotspot, creating this string of volcanic eruptions. While the plate passed over the hotspot, the hotspot melted most of this passage and afterwards, this region sank down from the cooling. It is a noticeable plain, devoid of mountains like the surrounding regions. Later, when the western US started to expand, which produced the Basin and Range region, this valley was susceptible to expansion, pulling the plate apart here. That expansion, which thinned the North American crust, combined with the low lying valley, allowed the hotter mantle to heat up this region melting the upper crustal rocks. This produced a score of volcanoes within the valley, including many parts of the western US down through Arizona. 

These volcanic eruptions, many of which were cinder cones, layered the Snake River Plain with scoria deposits. Later lake and river deposits made this valley an extremely fertile region with well drained soil, perfect for vineyards. Hence the reason so many wineries are located within the Snake River Plain.