 Complete the following phrase:  There is evidence of a large sector collapse on San Pedro, which removed the northwestern flank of the volcano and formed a large debris avalanche deposit. This avalanche deposit covers a surface area of and its front is high in the Pampa de la Avestruz. The debris flow formed by the sector collapse does not have many of the typical hummock-like hills of volcanic sector collapse deposits and instead features grooves and radial ridges. Such flank collapse occurred notably on Mount St. Helens during 