What is the difference between sills and dikes

Dykes are classified as discordant intrusions — they are not parallel but run across the preexisting land- or rock form. On the other hand, sills are formed in the same way as dykes, but their direction is different. Dykes are created in between and parallel to their surrounding bedding plates. Meanwhile, sills are often uniform in orientation since the surrounding rocks can give consistency to their form.

However, they can also be non-uniform in appearance in terms of color and direction. Sills are usually composed of medium-grained rock and often contain certain rare types of ore deposits in their formation. As an intrusion, a sill as a body of rock is concordant because it is parallel to the original rock or land from.

Dykes or dikes are igneous rocks that intrude vertically or across , while sills are the same type of rocks that cut horizontally or along in another land or rock form. Dykes are discordant intrusions, while sills are concordant intrusions. Dykes and sills form due to pressure, force, and stress from one point of origin. Dykes form when the point of origin is beneath the forming dyke, while sills are formed when the starting point is either on the left or right side.

Sills occur in parallel to the bedding of the other rocks that enclose them, and, though they may have vertical to horizontal orientations, nearly horizontal sills are the most common. Dykes and sills form due to pressure, force, and stress from one point of origin. Dykes form when the point of origin is beneath the forming dyke, while sills are formed when the starting point is either on the left or right side.

Both dykes and sills can be magmatic or sedimentary in nature. Sills: form when magma intrudes between the rock layers, forming a horizontal or gently-dipping sheet of igneous rock. A laccolith is found in the Hawaii volcanoes which were formed a long time ago but only erupted a few decades ago. Dykes or dikes are igneous rocks that intrude vertically or across , while sills are the same type of rocks that cut horizontally or along in another land or rock form.

What is the difference between a dike and a sill? Dikes are formed across vertical cracks, and sills are formed across horizontal ones. Please log in to add an answer. Continue reading The best way to discover useful content is by searching it.

Engineering in your pocket Now study on-the-go. Because sills generally form at shallow depths up to many kilometers below the surface, the pressure of overlying rock prevents this from happening much, if at all.

Lava flows will also typically show evidence of weathering on their upper surface, whereas sills, if still covered by country rock, typically do not. Figure 5. Certain layered intrusions are a variety of sill that often contain important ore deposits. Precambrian examples include the Bushveld, Insizwa and the Great Dyke complexes of southern Africa, the Duluth intrusive complex of the Superior District, and the Stillwater igneous complex of the United States.

These intrusions often contain concentrations of gold, platinum, chromium and other rare elements. Despite their concordant nature, many large sills change stratigraphic level within the intruded sequence, with each concordant part of the intrusion linked by relatively short dike-like segments.

Such sills are known as transgressive, examples include the Whin Sill and sills within the Karoo basin. Improve this page Learn More. Skip to main content. Module 9: Volcanoes. Search for:. Reading: Dikes and Sills Dikes Figure 1.

Figure 2.