In order of size:
A pile
A hill
A mountain
An island
A state/territory
A country
A continent
A moon
A planet
Some of these can be in different orders. Land is not often used in the context of a moon or planet, but can be.
A large land mass is commonly called a continent.
A large gathering of people is called a group, mob, crowd or a mass.
An Island
The earth started as one large land mass and it was called Pangea
Island
mass
pangea
A large land mass that protrudes out from a continent is called a Subcontinent. One example of subcontinent is India.
The mass movement in which materials move as one large mass is called a landslide. It occurs when the force of gravity overcomes the strength of the materials holding the slope together, causing the mass of material to move downhill.
A large mass of coral is called a coral reef. There are usually many organisms living in or surrounding the coral reef.
Pangea
depends what you mean by large - a continent is a large land mass for example