As one commentator mentions, The different colours are all from one pit! from left to right:

• LFH: - this is the leaf layer (O in USDA system). It’s comprised of fallen and dead organic matter at different stages of decomposition.

• Aegj: - this is the first mineral horizon encountered (A). The ‘e’ denotes that it’s had something leached out of it (iron in this case). the ‘gj’ indicates that mottling (due to periodic ground water inundation and subsequent oxidation of Fe2+ iron ions) is present. This particular soil profile was in the vicinity of a peatland. In fact, the region I dug this pit is comprised of 60% peat!

• Bmgj: this second horizon encountered (B). the ‘m’ in our classification system indicates very minor changes from the parent material (C horizon). ‘gj’ is defined above. the iron from the Aegj horizon was deposited here, which is why it’s brighter than the Ckgj horizon. However, it’s not enough to earn it the ‘f’ or ‘fj’ suffix, which would indicate that the iron deposition was a major forming factor in this profile.

• Ckgj: this is the last mineral horizon encountered ©. the ‘k’ indicates the presence of carbonates; ‘gj’ defined above.

This soil profile is common to somewhat wetter sites; typically a mix of aspen and white spruce. Occasional black spruce may be present.

Those are the different soil horizons, which are basically just layers of soil with different properties. If you’re interested in checking out actual soil profiles, the NRCS Web Soil Survey is a super cool website for the US.

My uneducated guess is that the left is the nutrient rich topsoil and deeper layers to the right. Still just a guess.