The Rhone valley is one big « leftover » result of the different fault lines between the Central mountains (Massive Central) and the Alpes. Adds to the fact that during the last Ice time, a glacier, is pushing itself west-words out of Switzerland, meets the Central Mountains and can?t get over that, so it is pushing itself further to the south, with its most southern point lying around Lyon. 12.000 years ago the ice starts to melt, and huge ice and water masses are sinking down towards Marseille
                                             
At certain places the Rhone river was 15 miles (30 km wide).
How strong its forces are is perfectly to see when standing on the famous hill side of Hermitage (picture below) (Tournon/Tain-Hermitage), where on one side the partly basalt hill of Hermitage, was in fact connected with the same basalt slope from St Joseph at the other side. It is still mind-boggling, how the river was able to cut through this solid type of rock, instead of pushing the alluvial deposit of the Hermitage hill.
It must have been, and sometimes still is, a fearing river that carves itself over a bit more than 100 miles (150-200 Km) towards the south leaving a larger becoming delta, finishing with complete flatland in the Camarque area, west of Marseille.
The finer sand, clay particles brought as a deposit over thousands of years to this area makes this flat land unique by floral and animal live.
Further north, from Orange to Chateauneuf du Pape, Tavel and even into the regions around Nimes, we see the end result of this ?alluvial deposit?, by smooth rolled river rocks. Up to five feet deep (1.5-2 meters). You? re standing in the old river bed of the Rhone,  as far as your eyes can see
The bright yellow stones are made from the hardest stone you can find and is called Silex, and we know a special place in Switserland where they are comming from. Overtime, the silex has been grinding softer stones , like a coffee grinder, and that is the soil that we find underneath and where the vines nourish on. Famous is the effect, that the stones capture the heat throughout the day and radiate the heat back at night. We do not have a lot of rain ( two feet (700 mm) average a year) but we can have spectacular thunderstorms. At least with this type of soil, you have very good drainage. As the heat reflection is very strong on the top-level, that means it stays rather ?cool? underneath the stones, and therefore the vines are stressed to do their utmost to find some moisture.