Photo: George Steinmetz
That is an ice tower (fumarole [wiki]), and Mount Erebus in Antarctica has hundreds of them:
The flanks of Erebus are spiked with ice towers, hundreds of them, called fumaroles. Gas and heat seeping through the side of the volcano melt the snowpack above, carving out a cave. Steam escaping from the cave freezes as soon as it hits the air, building chimneys as high as 60 feet.