Passage: The nearby San Andreas and Hayward Faults are responsible for much earthquake activity, although neither physically passes through the city itself. The San Andreas Fault caused the earthquakes in 1906 and 1989. Minor earthquakes occur on a regular basis. The threat of major earthquakes plays a large role in the city's infrastructure development. The city constructed an auxiliary water supply system and has repeatedly upgraded its building codes, requiring retrofits for older buildings and higher engineering standards for new construction. However, there are still thousands of smaller buildings that remain vulnerable to quake damage. USGS has released the California earthquake forecast which models earthquake occurrence in California.San Francisco's shoreline has grown beyond its natural limits. Entire neighborhoods such as the Marina, Mission Bay, and Hunters Point, as well as large sections of the Embarcadero, sit on areas of landfill. Treasure Island was constructed from material dredged from the bay as well as material resulting from the excavation of the Yerba Buena Tunnel through Yerba Buena Island during the construction of the Bay Bridge. Such land tends to be unstable during earthquakes. The resulting soil liquefaction causes extensive damage to property built upon it, as was evidenced in the Marina district during the 1989 Loma Prieta earthquake. Most of the city's natural watercourses, such as Islais Creek and Mission Creek, have been culverted and built over, although the Public Utilities Commission is studying proposals to daylight or restore some creeks.

Question: What made the Treasure Island?
material dredged from the bay as well as material resulting from the excavation of the Yerba Buena Tunnel