Ravine

A ravine is a specific type of landform shaped by the movement of water. It is defined as a narrow, steep-sided valley. Geologists often classify ravines by comparing them to other landforms. A ravine is larger in scale than a gully. However, it remains smaller than a canyon. These features are known as fluvial slope landforms. This means they are created by the action of flowing water.

Because they are shaped by water, they are also called fluvial landforms. They typically have steep sides with a gradient between twenty and seventy percent.

The formation of a ravine is a step-by-step process of erosion. Erosion occurs when water wears away the earth over time. This process often begins with gullies in hilly or mountainous regions. In these areas, water runoff is guided downhill by steep slopes. As the water flows, it carves into the landscape. A ravine represents the final stage of this gully erosion. When a stream erodes the earth so severely that it forms a deep cut, the gully becomes a ravine.

Ravines may contain different types of water systems. Some ravines have active streams flowing along the downslope channel. However, many ravines are characterized by intermittent streams. An intermittent stream is one that only flows sometimes. This happens because the geographic scale of a ravine may not be large enough to support a perennial stream. A perennial stream is a body of water that flows all year round. The presence or absence of these streams depends on the size and depth of the landform.

Different cultures and languages use various names for these features. In South Africa, a ravine might be called a kloof. On the Isle of Wight, they are known as a chine. Other names include a cleuch, a dell, a ghout, a gill, a ghyll, a glen, or a gorge. While many people use these terms interchangeably, some societies make a distinction. This distinction is particularly important for environmental management. Knowing whether a feature is a gully or a ravine helps experts manage the land.

Ravine erosion has significant environmental impacts. This process contributes heavily to land loss across the globe. It specifically threatens agricultural lands used for farming. When soil is lost to erosion, it can cause pollution and flooding. This happens because the lost soil causes the sedimentation of waterways. Sedimentation is when soil fills up the bottom of a river or stream. Human activities can also speed up this process. Deforestation, or the clearing of forests, and overgrazing by animals can make ravines form faster.

In the badlands of India, soil erosion is estimated to exceed a very high rate annually.

In Hawaii, the shield volcanoes create unique ravine systems. The volcanoes Mauna Loa and Mauna Kea have a major impact on how ravines are distributed. Mauna Loa is one of the most active shield volcanoes on Earth. Both volcanoes show V-shaped ravines on their flanks. These ravines appear only where the volcanoes have been mantled by Pahala ash. Mauna Kea is the older of the two volcanoes. Because it is older, it shows more pronounced dissection, which means the ravines are more deeply cut.

The way valleys begin in Hawaii depends on rainfall and infiltration capacity. Infiltration capacity is how much water the ground can absorb. Once these valleys are started, streams incise the land to form V-shaped ravines. Eventually, these can become deep ravine systems that expose groundwater activity. The deepest incisions are not V-shaped, but U-shaped. These are known as theatre-headed valleys. This shows how a single landform can change as it grows deeper and older over time.