When a volcanic eruption occurs at the surface, would the magma move through the crust to form a dyke or a sill? Explain your answer.
Some help from Internet:
Dykes are ingenous rocks that invade vertically w sills are the similar rocks that cut horizontally in rock form. Dykes are divergently invade while sills are clear intrusion. Dykes form when the point of origin is beneath while sills are formed when starting point is either on the left or right side.
To the sill
or dyke to form, the magma must first have enough pressure and force to break through the existing rock layers. This happens when the magma chamber deep within the earth builds up enough pressure to push the magma upward.
Whether a dyke or a sill is formed depends on the orientation of the cracks or existing rock layers that the magma encounters as it moves through the crust. A dyke forms when the magma cuts directly through the existing rock layers and moves vertically upwards towards the surface.
A sill, on the other hand, forms when the magma moves between the existing rock layers and spreads horizontally. This happens when the magma encounters a layer of rock that is weaker than the ones above and below it, and it can move through a crack in that layer.
So, whether a dyke or a sill forms depends on the direction of the magma's movement and the orientation of the layers of rock it encounters along the way.
When a volcanic eruption occurs at the surface, the magma typically moves through the crust to form a dyke rather than a sill.
To understand why this happens, it's important to understand the difference between a dyke and a sill. A dyke is a vertical or near-vertical intrusion of magma that cuts across the layers of the Earth's crust. It forms when magma is injected into pre-existing fractures or weaknesses in the rock, and then solidifies. On the other hand, a sill is a horizontal or near-horizontal intrusion of magma that occurs parallel to the layers of the crust. It forms when magma is injected between the layers of the rock and solidifies.
During a volcanic eruption, magma is generated deep beneath the Earth's surface in the magma chamber. As pressure builds up within the chamber, the magma seeks a path of least resistance to escape. It starts to rise towards the surface, creating a conduit known as a volcanic vent or pipe.
As the magma moves upward, it encounters the overlying layers of the Earth's crust. The crust is made up of various types of rock, including sedimentary, igneous, and metamorphic. It is characterized by fractures, faults, and other weaknesses that can provide pathways for magma to move through.
When the magma reaches these fractures or weaknesses, it starts to exploit them, creating a dyke. The magma intrudes vertically or near-vertically into the fractures, following the path of least resistance. It cuts across the layers of the crust, as it moves from the magma chamber to the surface.
The reason why a dyke is more likely to form during a volcanic eruption is that the vertically oriented fractures in the crust generally offer the least resistance to magma movement. The vertical orientation allows the magma to rise more efficiently, while encountering less resistance from the surrounding rock. In contrast, horizontally oriented weaknesses in the crust are less common and usually do not offer an easy path for the rising magma. This is why sills, which require horizontal or near-horizontal pathways, are less commonly formed during volcanic eruptions.
Overall, when a volcanic eruption occurs at the surface, the magma typically moves through the crust to form a dyke, taking advantage of pre-existing vertical or near-vertical fractures in the rock.