The rock cycle is the name for a single-track, two-wheeled vehicle powered by foot that was popular in northern Europe during Neo-neolithic times. Styles of rock cycles vary depending on the task for which they are designed and which materials they were made from.
History of the Rock Cycle
Originally designed by stonemason enginners during the Neolithic, it was originally built after nomadic hunter gatherers were suffering after walking up to 30 miles per day. However, this claim is also held by later Viking settlers in Denmark who are reported to have developed this revolutionary device, only to find that it doesn't work particularly well in flat regions (especially Denmark), forcing them to develop the longboat and sail from place to place. However, only the frame for the rock cycle was created during the Neolithic as the wheel was not discovered until the late Neo-neolithic where the discovery of limestone allowed for easier sculpting for a rounder wheel and hence a more enjoyable ride.
The rock cycle entered a new innovative age of design during the Bronze Age where nuts and bolts were first developed, allowing the pieces of rock to be held together and spin around a central axel without chipping or fracturing. This replacement of the original flint model however reduced the fractures and hence sparks which to that time had been the earliest known example of primitive headlights, albeit they were found on the wheels. The rock cycle was widely used across the north of Europe (except both Denmark and Holland for obvious reasons) until the Dark Ages when the first early bicycle model was put on the market by Sir Walter Raleigh. Pedal-power soon lost out to petrol as a popular method of transport and after the Netherlands had gone several ages without the rock cycle, the new bicycle became an exceptional craze in the lowlands, a phenomenon which stills occurs to this day.
How it Worked
Quite a simple piece of engineering genius, two large stone wheels were held together by a stone body which had a stone seat carved into the top. Two stone pedals where then attached to the main stone body by a strong connection (often a woolly mammoth tusk or antler). The rock cycle would then be taken to the top of a stone (or grassy hill, although grass proved to be more resistant) and pushed down the hill. Occassionally a large animal would then be tied to the front of the rock cycle using dead animal sinew which could then drag the rock cycle back uphill on the return-leg of the journey.
Rock cycles are of particular interest to geologists as the rocks forming the wheels of the rock cycle have been known to change given different speeds (similar to the Burning Rubber Theory). When the wheel of a rock cycle is rotated faster, friction against the ground creates heat and evidence for pseudometamorphism has been found. The most common example found is for limestone wheels to heat up and partially form marble at speeds in excess of 65mph. The diagram on the left illustrates this transformation from a sedimentary to a metamorphic state, although if the wheel is rotated in the opposite direction (shown in red), the rock transformation also occurs the opposite way (metamorphic to sedimentary).