It's called a volcanic sill.
They include batholith, lopolith, sill, phacolith, laccolith and volcanic neck.
The slab of volcanic rock that is formed when magma forces itself across rock layers is called a dike. This will eventually build into mountains.
a tabular body of intrusive igneous rock, ordinarily between beds of sedimentary rocks or layers of volcanic ejecta.
A sill (assuming you are talking about horizontal layers of rock)
One can find a window sill at a website called Amazon. You can also find them at some lumberyard or building supply. You can also find them at local hardware shops.
Volcanic islands are formed by volcanoes and are therefore composed of volcanic rock.
Forms of igneous rock are usually made. It is also known as lava rock and volcanic rock
A Sill is formed when a fluid rock (usually magma but it can be mud or salt) is squeezed in between the layers (usually horizontal) of older rocks before it solidifies in place. A Dike or Dyke is the opposite, here the fluid rock penetrates across the layering of the older rocks. Logically to get the material to form a Sill there must be an accompanying feeder Dyke.
R. H. Ridler has written: 'Petrographic study of a Crow Lake ultrabasic sill, Keewatin volcanic belt, northwestern Ontario'
Which volcanic feature did you find most difficult to identify? Explain why.
No idea