Years later, someone built a pig sty onto it and drained the pig sty into the nettle patch. Later still, the original wall blew over and so on. Each event, which may have taken a short or long time to accomplish, leaves a context, a deposit of material, on the site.
Over time, someone built a pig sty onto the existing structure, draining the pig sty into the nettle patch. The original wall eventually collapsed, and so on. Each event, regardless of its duration, creates a historical record by leaving behind traces of materials at the location.