The volume of the cone is calculated by the formula:
V = B*H/3
r=D/2 = 6/3 = 2
where B is surface area of basis and H is height.
B is circle which fomula for surface is:
B = r^2 * pi = 3^2*3,14 = 9*3,14 = 28.26
from condition of height we write:
H = 3*D = 3*6 = 18
now volume is:
If we express all of that in equation of volume we get:
V = 1/3* 3^2*3,14*18
When it's beneath the surface, the molten rock is called magma. When it reaches the surface, it erupts as lava, ash and volcanic rocks. With each eruption, rocks, lava and ash build up around the volcanic vent. The nature of the eruption depends on the viscosity of the magma.