Top 10 Interesting and Fun Facts About Mountains, Valleys, and Caves
1. What Is a Mountain?
A mountain is an area of land raised up from the earth's crust by tectonic plate movement and/or volcanic activity. There are four main types of mountain:
- Fold Mountains
- Fault-Block Mountains
- and Dome Mountains
Each of these types of mountain is formed in a particular way. Let's take a look at each of them in turn.
When two of the earth's tectonic plates collide, the crust at the plate edges may crumple and fold under the strain, pushing up ranges of fold mountains.
A volcano forms when magma (molten rock) from deep inside the earth erupts on to the surface, building into a tall cone. Some of the world's highest mountains are volcanoes.
Plate movements may squeeze layers of rock until they crack and snap. These cracks are called faults. Mountains form when a slab or block of rock is squeezed upwards.
The diagram below shows five phases in the formation of a fault-block mountain.
- Layers of rock form from deposited sediment and/or volcanic activity
- Tectonic plate movement causes the layers to lift and buckle
- At the highest stress point, a fault line emerges when the rock cracks
- As the rocks break, one layer slides over the other
- Over millions of years erosion alters the surface of the thrust-up rock, forming a mountain range along the fault line
A large up-welling of molten rock beneath the earth's surface, called an igneous intrusion, may force up the overlying layers of rock into a huge bump. Mountains formed in this way are called dome mountains.
2. Where Are the World's Major Mountain Ranges?
The map below shows the approximate locations of the world's major mountain ranges. These ranges are not only the highest but also the longest ranges of mountains in the world.
You may be interested to note that most of them follow the edges of the earth's tectonic plates.
Map of the Longest Mountain Ranges in the World
Key to the Map
- Aleutian Range - 2,650 km (1,650 miles)
- Rocky Mountains - 4,800 km (3,000 miles)
- Andes - 7,200 km (4,500 miles)
- Brazilian Atlantic Coast Range - 3,000 km (1,900 miles)
- Tien Shan - 2,250 km (1,400 miles)
- Himalaya/Karakoram/Hindu Kush - 3,800 km (2,400 miles)
- West Sumatran Java Range - 2,900 km (1,800 miles)
- Central New Guinea Range - 2,000 km (1,240 miles)
- Great Dividing Range - 3,600 km (2,240 miles)
- Trans-Antarctic Mountains 3,500 km (2,200 miles)
3. The Life of a Mountain
Mountains are considered to have a "life cycle" much like living things. The life of a mountain is divided into three phases. These are:
- and ancient
Let's look at each in turn.
A Young Mountain
Mountains that formed during the last few million years, or that may still be growing, such as the Himalayas, are considered to be young mountains.
A Mature Mountain
Mountains which are already several hundred million years old and have been eroded to a fraction of their original size, such as the Urals, are called mature mountains.
An Ancient Mountain
Mountains that have now been eroded so far that they have become little more than hills along a low-lying plain are considered to be ancient mountains.
4. Which Are the World's Highest Mountains?
Height in m (feet)
5. Biological Zones of High Mountains
High mountains have a range of biological zones based on altitude. In the lower zones, biodiversity is greatest, often with lush vegetation and a wide range of animal and insect life, while in the highest zones, it may not be possible for any form of life to survive due to the dramatic drop in temperature and the lack of oxygen.
Diagram of Biological Altitude Zones
- Wide range of vegetation and wildlife
- Broadleaf forest
- Pine forest
- Only specially adapted high-altitude species can survive
- "Dead Zone" where nothing can survive
Valleys and Caves
The forces of erosion, as we have seen with mountains, are constantly attacking the land and changing its appearance. Rain flows down from mountainsides into rivers that carve the landscape with valleys. In limestone areas, rain seeps into the rock substrate, eating it away to form caves.
6. Fascinating Features of a Valley
A river valley usually begins in the mountains as a steep-sided gully cut by a fast-flowing stream. As it flows down towards the lower ground, the river slows down and the valley widens. As it nears the sea, the river flows across a wide, level flood plain. Some rivers fan out into a delta at their estuary.
The Beginnings of a Valley
The river valley begins high in the mountains as a narrow gully.
A V-Shaped Valley
In the river's upper course, the valley has a characteristic V-shape.
A Meandering River Valley
Once it reaches the flat plains, the river meanders back and forth as the rate of flow slows down, widening the valley.
Where the River Meets the Sea
Where the river meets the sea, the valley flattens, typically covered in a thick layer of sand and mud. At this point, the river flows out into an estuary, or broadens into a fan shape known as a river delta.
7. Types of Valley
There are four different types of valley. They are:
- and Wadi
Let's examine each in turn.
In glaciated areas of the world, deep valleys are scoured out by glaciers. When a glacier melts, for example at the end of an ice age, the sea level may rise, flooding the valley to form a fjord.
Rift valleys form when a long, narrow block of land sinks between two faults, at places where two tectonic plates are pulling apart.
Gorges and Canyons
A gorge is a deep ravine with walls that are almost vertical. A canyon is also a gorge, but usually with water flowing through, found in the desert. The source of its river is often outside the desert.
A wadi is a narrow, steep-sided desert valley that is usually dry. A wadi's characteristic shape is carved out by the flash floods that occur after torrential desert rainfall.
8. How Are Caves Formed?
Caves are large, naturally occurring hollows in the ground, in cliffs, or in ice. There exist four main types of caves. They are:
- Limestone Caves
- Sea Caves
- Ice Caves
- and Lava Caves
Let's explore each in turn.
Most caves occur in limestone areas, because this type of rock is soluble (it dissolves) in rainwater.
Sea caves are formed when waves crash against the coastal rocks. Over time this wave action erodes the rock at its weakest points and caves are slowly carved out.
Ice caves are formed by streams of warmer melt-water running beneath a glacier. In time, this can result in a cave in the ice.
When the crust of a lava flow hardens, the molten lava beneath may flow out, leaving a hollow. This is how lava caves are formed.
9. Fantastic Features of Limestone Caves
Limestone caves are the most common and often the most dramatic and interesting caves.
Water dripping in limestone caves leaves behind tiny amounts of calcite. These mineral deposits build up to form distinctive limestone cave features. These are known as stalagmites (if they grow up from the ground) and stalactites (if they grow down from the "ceiling"). It can take from four to four thousand years for a stalactite or stalagmite to grow one inch (2.5 cm).
10. Record-Breaking Valleys and Caves
The Longest Fjord
The longest fjord is the Nordvest Fjord in Greenland, which extends 313 km (194 miles) inland from the sea.
The Largest Gorge
The world's largest gorge is the Grand Canyon in Arizona, USA. It's 394 km (217 miles) long and up to 1,676 m (5,499 feet) deep.
The Largest Cave Chamber
The largest cave chamber is the Sarawak Chamber in Sarawak, Malaysia. It boasts an area of 162, 700 m2 (1,751,300 square feet). The chamber is 700 m (2,300 feet) long, and has an average width of 300 m (980 feet). The lowest part of the roof is 70 m (230 feet) high.
The Longest Cave System
The longest cave system in the world is the Mammoth Cave System in Kentucky, USA. It's 560 km (348 miles) long.
The Longest Stalactite
The world's longest recorded stalactite is found in "Poll an Ionana", a cave in County Clare, Ireland. The stalactite is 6.2 m (20 feet and 4 inches) long.
The Tallest Stalagmite
The world's tallest stalagmite is found in the Krásnohorska cave in the Czech Republic. It stands a lofty 32 m (105 feet) from the base.
A Last Word
So, we've been up mountains and down valleys, and even deeper down into all kinds of caves. I hope you've enjoyed the journey and picked up some fascinating and fun facts along the way. The study of how mountains, valleys, and caves are formed is all part of geography and geology, more widely known as Earth Sciences. Earth scientists, women and men from all over the world, are hard at work every day discovering new information about our amazing planet. Maybe one day you'll join them.
© 2019 Amanda Littlejohn