Dyke
Also called: Dike · Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 11, Ch 3 "Interior of the Earth"
Meaning
A dyke is a wall-like body of igneous rock. It forms when magma forces its way into cracks in the rock and sets almost upright. A dyke is discordant: it cuts across the rock layers instead of lying along them. Dykes are often the channels that carried magma up to the surface during fissure eruptions. Dyke rock is often harder than the rock around it. Erosion can then leave dykes standing out as long, narrow ridges.
Example
Western Maharashtra has many dykes. These are the old feeder channels that brought lava up to build the Deccan Traps.
Don't confuse with
- Sill: also sheet-like, but almost horizontal and concordant (it lies parallel to the rock layers). A dyke is almost upright and cuts across them.