1. Geosphere
The geosphere is the Earth itself, the rocks, minerals, and landforms of the surface as well as its interior. Geo- means Earth.

2. Parts of the Geosphere and how much it covers the Earth
The outermost layer of the Earth is the crust – the cooled and hardened part of the Earth. The depth of the crust varies from 5 km underneath the oceans and 30 km thick underneath the continents. You might be surprised to know that the Earth's crust only accounts for about 1% of the entire volume of the Earth.

3. Interactions
(Atmosphere) When the volcanoes erupt, they produce many carbon dioxide and other gases which then will be released into the atmosphere.
(Biosphere) As long as humans don’t interfere, the equilibrium is balanced. The greenhouse effect is caused by the gases which originated in the geosphere. This controls the temperature of the earth thereby making the biosphere climate moderate.
(Hydrosphere) When these two spheres interact with each other it creates underwater volcano's.