Ushishir consists of two islets almost connected by a narrow spit of land with an area of . These islets are the tops of a partially submerged volcano. The southern island,
Yankicha (), consists of the summit caldera and has a maximum width of . The caldera has a diameter of , and is breached on the south, forming a sea-water
Crater Bay. The bay has an estimated depth of , and there is strong evidence of ongoing
underwater volcanic activity, as evidenced by frequent bubbles, altered water chemistry and the presence of bacteria mats. Two small
lava domes form small islands in the central lagoon, and numerous
fumaroles and hot springs are along the southeast caldera shoreline. The island's highest point is high, and is on the eastern shore. The northern islet (
Ryponkicha ) is the smaller of the two, and consists of a portion of the volcano's flank, with sheer cliffs rising up from the sea. Ushishir is an
active volcano with the last known
eruption in 1884. ==Fauna==