When it comes to rock 'n' roll, many layers make up the workings of the music. From its earliest days when country and R&B converged for a new, wilder hybrid to its evolution over the decades including punk, metal and roots, there's never been just one single shade to rock 'n' roll.

But it's all part of the natural progression. The blues-based rockers of the '60s slowly gave way to heavier music mid-decade; bands such as Yardbirds, Cream and the Jimi Hendrix Experience laid the foundations for a new music that would dominate much of the '70s': hard rock.

As you will see in the below list of the Top 35 Hard Rock Albums of the '70s, even this singular subgenre has its offshoots, and it's not quick to be defined. (Our criteria? We know it when we hear it.) From leftover pieces of the previous decade to the birth of heavy metal, hard rock music has always had more textures to it than it lets on. Finding a line between the Who's stately rock operas and AC/DC's bad-boy boogie isn't always easy, but dig deep enough, and a pattern will begin to reveal itself.

READ MORE: Top 40 Soft-Rock Songs

Familiar names show up often, more than just one or two times, in the Top 35 Hard Rock Albums of the '70s, which were chosen by the UCR staff. Led Zeppelin, Aerosmith and Black Sabbath place several records in the upper half; there are even some surprises among the candidates.

Yet they all have one thing in common: the outlining structure of rock 'n' roll amplified through the sheer force of their music and, especially, the guitars at the center of much of it. For better or worse, hard rock turned into something else during the following decades. But here, in its '70s glory, there was rarely music as exciting and significant to the genre's progress.

Top 35 Hard Rock Albums of the '70s

From holdover electric blues to the birth of heavy metal, these records pretty much summed up the decade.

Gallery Credit: Michael Gallucci

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