Wensleydale is a long, open and broad dale gently rising to the flat topped hills that enclose it and give it its individual character. Until the beginning of the 18^th century the name Yoredale, or Uredale after its river, the Ure, persisted alongside the name Wensleydale, after Wensley, an important market town up until the middle of the 16^th century.

Beneath Wensleydale, 500m below the surface, is a pink granite, known as Wensleydale Granite, which is some 400 million years old. About 350 million years ago the Great Scar Limestone was deposited upon the eroded surface of the granite. This is now only visible from Dysart to Appersett along the valley floor, but is also present at Raydale and Bishopdale although here it is mostly covered by glacial deposits.

On top of the limestone lies the Yoredales, which comprise a repeated series limestone, shale and sandstone layers. In 1835 the geologist John Phillips chose Wensleydale as his type area and hence the name Yoredales was derived. The Yoredales vary in thickness at different locations within the dales but at Askrigg, for example, they are 275m deep. 

The Yoredales are primarily responsible for the unique landscape in Wensleydale. The easily eroded shales form the gentler slopes of the valley sides, the harder limestones exposed as horizontal scars and steps on the valley sides, such as the prominent step of Hardraw limestone upon which the village of Thornton Rust is built. The Yoredales have also given rise to numerous waterfalls in the dale, formed by alternating beds of hard limestone and sandstone within the soft shales. The best example is Hardraw Force with the highest single drop (27m) in England. Mill Gill Force and Whitfield Force are of similar origin.

High Scars such as Ellerkin Scar near Askrigg and High Clint near Hardraw have been formed by the 22m thick Main limestone from the Upper Carboniferous period that lies above the Yoredale series. The Main limestone also caps the flat-topped hills, such as Crag Hill and Wether Fell. On top of this is a bed of chert mixed with limestone. Chert was quarried at Flint Hill for use in the ceramic industry.

Millstone Grit outcrops on top of the fells to the north and south of the dale, including Dodd Fell, Penhill, Great Haw and a small patch on Wether Fell and more widely on Great Shunner Fell to the north. Coal seams have been worked in places, as on the sides of Great Shunner Fell.

Uplift of the granite about 330 million years resulted in faults in the overlying rock strata, allowing the formation of mineral seams including lead ore, calcite, fluorite, barite and other minerals, some of which have been exploited in the past.

There are numerous sink holes and swallowholes on the upper surfaces of the limestone and springs lower down where the streams reappear at its foot, for example above Thornton Rust.

The Ice Age impacted upon Wensleydale by carving out the u-shaped valleys, although each of the dales was affected differently. The main glacier in Wensleydale was less erosive than in some of the side valleys, such as Bishopdale, which contained a steep and active glacier leading to the significant deepening of the valley. Waldendale’s v-shape profile shows that it was little affected by ice.

As the glaciers retreated, deposits were left which exert a significant influence on the present day landscape. These include drift tails, relatively unusual features formed at the junction of tributary valleys. Comprised of glacial till, they are seen joined to the spurs of the tributary valleys and form long tails pointing downstream and are often moulded into drumlin-like shapes and tend to divert the incoming streams further to the east. This deflection of the tributaries is responsible for many of the waterfalls within the tributaries. Examples can be seen at Cotterdale Beck where a drift tail has contributed to the formation of Cotter Force, and Fossdale Gill is deflected over Hardraw Force and round the drift tail. There is a large drift tail between Bishopdale and Wensleydale.

Glacial drumlins can be seen between Hell Gill and the Moorcock Inn and around and including Brough Hill (on which a Roman Fort was sited) between Bainbridge and Aysgarth.

Lateral moraines occur on both sides of the river near Aysgarth and Bainbridge. At Aysgarth there is a conspicuous terminal moraine and another crosses the valley floor at Brown Moor almost two miles below Hawes. Both of these moraines created dams across the river and held back shallow lakes for a time; these now form part of the flat river flood plain in these areas. 

Semer Water is a natural lake of glacial origin, a rare feature and one of the largest in Yorkshire. It was dammed at its lower end by glacial debris and was formerly much bigger reaching further up Raydale; the overflow from the lake formed the gorge and falls of the River Bain above Bainbridge. The former course of the Bain at the Countersett end is blocked by a drift tail.

The River Ure has its source high on the side of Lunds Fell on the borders of Cumbria. At the Moorcock Inn, close to the dale head, the riverbed lies at 305m above sea level and from here to Kilgram Bridge at the lower end of the dale (a distance of 26 miles); the river drops 215m in height to just above 90m above sea level. About a third of this fall comes in the 3 miles between Redmire and Aysgarth with a series of waterfalls. Aysgarth Falls, one of the most popular tourist attractions in Wensleydale, were formed by a rise in the level of the land and are cut into thick limestones separated by thin shales that results in a stepped formation. Numerous other falls occur in Wensleydale including Cotter Force and falls at Gayle, West Burton and Widdale Beck, with many others on the tributary streams.

Soils that have developed in Wensleydale range from the rich, fertile loam and clay river alluvium and coarse loam and sand over gravel along the valley floors, to the fine loam and clayey upland soils with a very acidic peaty surface horizon. They closely reflect the underlying geology that varies considerably from bands of limestone, sandstone and shale to glacial till and floodplain river deposits. Landform has had an effect on soil development, the flat areas on tops of the fells and valley floors being poorly drained allowing the formation of peat, the slopes being better drained and supporting a richer flora. Lower down the slopes the soils are thicker and higher in mineral content.