Part of Discover Teesdale
our guide to the walks, waterfalls, history and peaceful places that make Teesdale special.

Geology of Teesdale

🪨 Introduction

Teesdale is one of those rare places where you can actually see the story of the Earth. Every cliff, scar and waterfall tells part of a tale that began hundreds of millions of years ago long before people, castles or villages. From fiery volcanoes to frozen valleys, Teesdale’s landscape was shaped by nature’s most powerful forces.

🌊 340 Million Years Ago – Teesdale Under the Sea

Back then, Teesdale wasn’t land at all, it was the bottom of a warm tropical sea filled with fish, corals and tiny shell creatures. As they died, their shells built up on the sea floor and turned into Carboniferous Limestone, which still lies beneath much of Teesdale today.

When you explore places like God’s Bridge or Summerhill Force, you’re standing on that ancient seabed, packed with tiny fossils from a time when Teesdale was underwater.

Summerhill Force

🔥 295 Million Years Ago – Fire Beneath the Dales

Around 295 million years ago, molten rock from deep underground pushed up between the layers of limestone. When it cooled, it formed a hard, dark rock called Whin Sill dolerite. This same rock stretches beneath Hadrian’s Wall and High Cup Nick.

The River Tees flows over this tough Whin Sill, while the softer limestone below erodes faster. Over thousands of years, that erosion caused the top rock to collapse piece by piece, creating the incredible step-shaped waterfall we call High Force.

Nearby Low Force Waterfall formed the same way. Together, they show how Teesdale’s volcano-born Whin Sill still shapes the landscape today.

High Force waterfall plunging over the Whin Sill dolerite cliffs in Upper Teesdale

❄️ 20 000 Years Ago – The Ice Age Arrives

During the last Ice Age, Teesdale was buried beneath huge glaciers. These rivers of ice carved out the wide U-shaped valleys we walk through today.

When the ice melted, torrents of meltwater cut new paths through the rock, uncovering the Whin Sill cliffs and leaving scattered boulders and smoothed rock as clues to the valley’s frozen past.

Holwick Scars cliffs showing the Whin Sill exposed by Ice Age glaciers.

💧 After the Ice – Rivers Shape the Valley

Why does Teesdale have so many waterfalls?

The answer lies in Teesdale’s unique mix of rocks. The Whin Sill dolerite is incredibly tough, while the limestone and sandstone beneath are much softer. The River Tees and its becks wear away those softer layers, forming a whole chain of waterfalls from High Force and Low Force to quieter spots like Bleabeck Force and White Force.

It’s one of the best places in England to see how geology shapes rivers in real time.

Low Force waterfall on the River Tees showing layers of Whin Sill above limestone.

🪨 Limestone Wonders and Caves

What type of rock is found in Teesdale?

Most of Teesdale sits on Carboniferous Limestone, laid down when this area was under a tropical sea. Above it lies the Whin Sill, a dark volcanic dolerite. Together, these rocks form the cliffs, caves and waterfalls that make Teesdale so distinctive.

Rainwater slowly dissolves the limestone, carving underground streams, caves and natural arches like God’s Bridge. Some springs even turn dissolved minerals into new stone — nature still building the valley today.

God’s Bridge natural limestone arch showing underground river erosion in Teesdale.

🌾 The Open Moorland – Teesdale Today

Above the cliffs and waterfalls lies Teesdale’s wild moorland, shaped by thousands of years of weather, peat and plants. Beneath the heather are layers of volcanic rock, glacial debris and ancient river deposits.

Walking here is like stepping across the pages of Earth’s history, from tropical seas to frozen tundra, all in one landscape.

Teesdale moorland above Holwick Scars showing heather and peat over ancient rock layers.

🌿 A Living Geopark

Today, Teesdale sits within the North Pennines UNESCO Global Geopark one of the world’s most important geological landscapes. Scientists, walkers and photographers visit to see how volcanoes, ice and rivers shaped northern England.

Every scar, beck and boulder has a story to tell — all you have to do is explore.

White Force waterfall in a peaceful Teesdale valley, part of the North Pennines Geopark.

💡 Quick Facts – Teesdale Geology

 

🪨 Oldest rocks~340 million years old

🌋 Whin Sill thickness Up to 70 metres

💧 Major waterfalls 10 + including High Force

❄️ Glacial valleys Formed ~20 000 years ago

🌍 Protected area North Pennines AONB & UNESCO Geopark

 

 

💧 Major Waterfalls of Teesdale

Teesdale is often called England’s Waterfall Capital, home to more waterfalls than anywhere else in the country. Each one exists because of the area’s unique geology, hard Whin Sill dolerite sitting above softer limestone.
Wherever the River Tees or its becks cut through those layers, waterfalls form.

Some of the best-known examples include:
High Force, Low Force, Cauldron Snout, Bleabeck Force, Summerhill Force, White Force, Black Force, and many smaller hidden falls scattered across the upper dale.

💡 Every waterfall tells part of the same story — how millions of years of fire, ice, and water shaped Teesdale’s dramatic landscape.

❓ FAQ – Common Questions About Teesdale Geology

How was High Force formed?

High Force Waterfall was created where the hard Whin Sill dolerite lies above softer limestone. The River Tees erodes the lower layer, causing the top to collapse and form a tall step-shaped fall.

Why does the River Tees have so many waterfalls?

Because the valley alternates between strong Whin Sill and softer rocks, water cuts down unevenly, making a whole chain of waterfalls through Upper Teesdale.

What is the Whin Sill?

The Whin Sill is a sheet of volcanic dolerite rock formed underground about 295 million years ago. It runs across northern England and appears at places like High Force and Hadrian’s Wall.

What type of rock is found in Teesdale?

Teesdale is built from Carboniferous Limestone, sandstone, shale and the Whin Sill dolerite. These layers explain its cliffs, caves and waterfalls.

Every rock, waterfall and scar in Teesdale tells a story millions of years in the making. From ancient seas to icy valleys and wild moorland, this landscape is living proof of how powerful and peaceful nature can be.

👉 Next: explore Teesdale’s Waterfalls
and see this incredible geology in action.

Explore more in Teesdale

See how the rocks shape waterfalls, walks and night skies: