The Basics

• Part 1 Geology and wine (Place)

• Part 2 Weather (Time)

Part 1 Geology and wine (Place)

At the heart of all wine growing regions are the soils and the rocks underneath. But it is the rocks under ground that set the scene for above ground. Some rocks are harder than others and weather differently, harder rocks often form the hills, while softer rocks weather faster and fill valleys. So the rocks beneath control the altitude, orientation and composition of the landscape.

The lay of the land can affect a number of climate issues, for example in Southern England a southerly sloping vineyard will receive up to 30% more sunlight in October compared to a flat vineyard. Not only that, a slope is also beneficial if you are in a wet region as much of the rain water will run off, minimising how much water is absorbed by the rocks and thus is available to the vine.
Rocks that have many small pores can hold water, protecting the vine from periods of drought. While rocks that have cracks throughout, allow water to pass through them, allowing the roots to stay dry. For example heavy clays have high porosity (hold water) but low permeability (ability to pass water).  This results in water soaked roots in wet countries, but in a dry zone they may hold enough water to let the vine have a good drink. Chalk usually has high porosity (holds water) and permeability (passes water) so in wet regions the roots will stay dry but should a drought occur, the vine still has access to water.

There are three types of rocks: Sedimentary, Igneous and Metamorphic.

• Sedimentary rocks are formed by layers of small particles forming into solid matter over time. These include sandstone and limestone.

• Igneous rocks are formed from volcanic eruptions. Rocks that are formed by the fast cooling of magma create basalt and rhyolite, while slow cooling forms other types of rock such as granite.

• Metamorphic rocks are rocks that are heated and may be subject to high pressure from being buried deep within the earth. The heated rocks create hornfels and granulite, while high temperature and high pressure create slate and schist.

Part 2 Weather and Climate

How cool is your climate? While many people talk about soils, the biggest single factor that affects a wine  after the grape variety is the climate.
If weather is the temperature, rain, sunshine, frost, even ultra violet rays on any particular day, then climate is a longer term average of these weather events. So, while the weather appears random from one day to the next, over the course of a season or year the climate is much more stable.

If we divide the world into two groups, cool climate and warm climate, we get a general feel for the style of wine able to be produced. Cool climate wines often exhibit lower alcohol, higher levels of acidity with fresh clean and defined aromas. Hot climate wines tend to produce wines that are higher in alcohol, lower in acidity and, if the climate is very hot or the grapes have been left on the vine for a long time, stewed baked flavours that can be hard to define.

Once you start to understand the climate of a region you can get a feel for the type of wines that can be made in that region.

By looking at a map you can start to understand the types of climate in the world. Most vines grow at between 30 and 50 degrees latitude in the Northern and Southern hemisphere. The equator is at 0 degrees and vine growing for wine making starts around 30. Here the climate tends to be hot, but as you move closer to 50 degrees latitude the climate is much cooler.

Now this is a good general rule of thumb, but we can easily improve on this. The closer you are to the sea the more moderate the temperature, as the sea helps to keep the land warm in winter and cooler in summer. Continental areas surrounded by land tend to heat and cool much faster tending to be warmer during the summer growing season and cooler in winter.  

One last general observation, is that west coast regions facing a significant sea or ocean often have more rain than inland and eastern coast regions. This is because the winds that drive much of the world's clouds travel from the west to the east dropping what rain they have when they hit land fall.

To put it all together the map above describes the world's climates on different wine growing regions of the world. You will see that occasionally grapes are grown outside the 30 50 latititude boundary for example England where the Gulf stream keeps us warmer than we normally would be. Other areas can grow grapes at higher latitudes but normally these are at a high altitude where the climate is cooler, such as Australia Granite belt in Brisbane.

Audio Interviews

Interviews are from the UK Wine Show on Terroir and wine . "Click to listen" to the interview only. The header will take you to the full show and its notes.