Step 1: Understanding the Concept:
The question asks to identify the major Earth Summit that took place in Johannesburg, South Africa.
Step 2: Detailed Explanation:
The major UN conferences on environment and development, often called Earth Summits, are:
\[\begin{array}{rl} \bullet & \text{First Earth Summit (1992): Held in Rio de Janeiro, Brazil. Also known as the United Nations Conference on Environment and Development (UNCED).} \\ \bullet & \text{Second Earth Summit (2002): Held in Johannesburg, South Africa. Officially called the World Summit on Sustainable Development (WSSD). It was a 10-year follow-up to the Rio Summit.} \\ \bullet & \text{Third Earth Summit (2012): Held again in Rio de Janeiro, Brazil. Known as the United Nations Conference on Sustainable Development (UNCSD) or Rio+20.} \\ \end{array}\]
Therefore, the summit held in Johannesburg was the second major Earth Summit.
Step 3: Final Answer:
The Second Earth Summit was held in Johannesburg.