The Humboldt Current carries cold water from the South Pacific to the equator -- all along the South American continent. It is both wide and long and creates cold weather conditions as it flows north. This leads to the formation of fog along the coastal regions of Peru, Chile, and Ecuador; and this cold air is carried into the interior by coastal breezes. As a result, it helps create conditions for cold climate grapes in coastal wine regions such as Chile's Casablanca Valley. The east-west-oriented valley is roughly 30km (20 miles) long and separated from the Pacific Ocean by the Coastal Mountain Range. This tempers the cooling effects of the ocean influences, but in the evening, the winds shift and air from the Andes continues to cool the valley. With a longer ripening period, the white grapes have more time to develop greater flavor complexity, while maintaining sugars and acids in balance. Thus the Casablanca Valley is well suited for both Chardonnay and Sauvignon Blanc. These vines are planted either along the eastern slope of the range or on the valley floor where the soils are rich in maicillo (coarse-grained particles of sand and gravel), clay, or granite bedrock.
Viña Morandé's Belén vineyard is located only fourteen miles from the sea and contains granite-rich soils with varying amounts of clay depending on height and location. The vineyard receives a mixture of cold and warm air with the morning mist lowering temperatures to allow Sauvignon Blanc to ripen slowly and obtain different profiles. For the Viña Morandé Gran Reserva D.O. Casablanca Valley Sauvignon Blanc 2020, the wine is partially aged on its lees providing noticeable weight on the finished wine. It also offers a slightly herbaceous and lemon aroma, followed by racy minerality and citrus flavors, and finishing with excellent acidity.
Matetic Vineyards is located in the Rosario Valley and is even closer to the Pacific Ocean, only six miles away, and thus receives some of the coolest temperatures in Casablanca. They farm biodynamically in the granite-rich soils of the Valle Hermoso vineyard and the Matetic Vineyards EQ Coastal Sauvignon Blanc 2020 is a blend of multiple fermented grape musts. The majority was fermented in stainless steel tanks where the wine then remained for four months sur lees. Around 30% of the grape must was fermented in concrete 700-liter egg-shaped vessels and another 30% was fermented in neutral oak barrels. This technique enhanced the mouthfeel and texture while still allowing the natural fruit and minerality to shine through. The wine shows both citrus and tropical notes with a similar herbaceousness as the Viña Morandé. Racy minerality as well. 
Casas del Bosque farms the La Cantera vineyard planted on the slopes of the Cordillera de la Costa mountain range -- 10 miles from the Pacific Ocean. La Cantera is named after an old granite quarry and is planted in the reddish soils rich in the granite rock, which also contains some iron and clay. Like at Matetic Vineyards, the climate is the coolest in Casablanca allowing the grapes in the Casas del Bosque La Cantera Sauvignon Blanc 2020, Las Dichas, Casablanca to develop slowly. The free-run juice is then fermented and rests on its lees for a couple months. This results in a delicious wine, mostly grapefruit and tropical with a touch of herbaceousness and a little less minerality.
