The Earth's four spheres interact in all six possible combinations: lithosphere and hydrosphere, lithosphere and biosphere, lithosphere and atmosphere, hydrosphere and biosphere, hydrosphere and atmosphere, and biosphere and atmosphere. All six interactions go in both directions, for example, from lithosphere to hydrosphere and from hydrosphere to lithosphere.
The Earth system consists of rocks, magma and core, called the lithosphere; all of its water as liquid, ice or gas, called the hydrosphere; the atmosphere or air; and living organisms, called the biosphere. The spheres get their energy and power from the sun and Earth's internal heat.
An event is a change to a sphere or the effect of a change in one sphere on a contiguous sphere. When an event in one sphere affects another sphere, it is called an interaction.
A classic example of an interaction between spheres is when a plant (part of the biosphere), takes carbon dioxide from the atmosphere and water (the hydrosphere) through its roots from underground (geosphere) to perform photosynthesis, which provides the plant with food and releases oxygen into the atmosphere.
Another example is when volcanoes (lithosphere) erupt. Dust and ash particles (lithosphere) spread through much of the atmosphere and block sunlight. Less sunshine can cause a cooler, drier climate in parts of the world. Cooler climate affects the biosphere by shortening the growing season.
Yet another example is soil erosion, which occurs when rain (hydrosphere) falls on land (geosphere) denuded of vegetation (biosphere) by fire or clear-cutting. Streams and rivers (hydrosphere) become muddy or murky from erosion.