What Causes Volcano To Erupt?

A volcano can be defined as a fissure in the crust of the earth erupting gases and molten lava. Volcano is a vent through which magma and dissolved gases are discharged. Magma forms when lower crust or the upper mantle of the earth melts and this magma is discharged in volcanic eruption.

Volcanic eruption is caused by three major factors. The first is buoyancy of the magma formed in the crust of the earth. When rocks melt in the crust of the earth forming magma, its mass remains the same, whereas the volume increases considerably. This magma rises towards the surface due to its buoyancy. The second factor is the pressure from the gases in the magma. Molten lava produces gases such as sulphur dioxide and carbon dioxide. As the magma rises to the surface, pressure from the gases within it increases resulting in volcanic eruption

The third factor causing a volcanic eruption is the injection of a new mass of magma into an already filled magma chamber. When a high volume of new magma enters an already filled magma chamber, the resulting high pressure creates a volcanic eruption.

I think the volcano gets mad and blows its top off,when pressure and gases from molten become very strong

Near subduction zones one plate is forced below another plate. This is caused by compressional forces. The rock is melted by the hot mantel and it is turned into magma. This magma then flows into cracks and fractures. The magma may reach the surface or it may cool to form intrusive rocks. Volcanoes are opening where the magma, gases and ash erupt. The hole is called a vent.

Volcanic eruptions is caused by new magma entering a chamber

It's the magma (lava) that comes up to the surface when it reaches a certain temp that creates it to explode.

Hi the answer is that the volcanic eruption is when the lava

A volcano could erupt when the tectonic plates rub together
OR
when new magma is ready to be pushed into the magma chamber which forces the old ones to spurt out the top to make room for the new ones.

A volcanic eruption only takes place when the hot rising magma deep down in the volcano wants to be free. In the Mount St Helens volcano, pressure would have started building up around March. This was indicated by the abrupt increase in earthquakes and the plumes of ash rising from the volcano. This was a definite signal to scientists that the volcano had come back to life. Because of the build up in pressure the magma was pushing and breaking the rock in the magma chamber to get to the surface. This is because of the magma being less dense than the surrounding rock and the increasing pressure from expanding gases. In the case of the Mount St Helens volcano the magma could not escape through the main vent because of unbreakable volcanic rock hardened by previous eruptions; and veered off in a dike. A dike is where the magma takes a different path to the surface. This dike grew into crypto dome (a chamber just beneath the surface). This chamber grew at an estimated 1.8m per day due to the increasing pressure. The rock 'lid'; the only thing stopping magma breaking the surface; was being crushed by the magma.

It is caused by the built up of hot magma that leads to the pressure inside the volcano to shoot up tremendously and so the volcano erupts, spewing up tons and tons of lava.

Because of earthquakes!