A Pakistani navy team travelled to the island on Wednesday. The island is 18 metres high, 30 metres long and 76 metres wide. EndFragment
18 metres high
76 metres wide
30 metres long
Officials have warned residents to stay away from the island, saying it could be emitting dangerous gases. 
Scientists speculate the formation could have been formed by a mud volcano. Mud volcanoes have formed in this same region in past years.   In November 2010, Pakistani fishermen reported that a new island had appeared in the Arabian Sea.  Drag the slider back and forth to see the Arabian Sea in 2010 on the left, and the emergence of the island in 2011 on the right. Scientists said the formation was likely a mud volcano, when the shifting Arabian plate heated up under intense pressure.  Volcanic gases and magma heated the groundwater and rocks melted into clay, according to NASA Earth Observatory.  The mud formation then seeped through faults and emerged as a mud volcano. About a year later, the island had vanished – washed away by the waves.  EndFragment    
(Source: USGS)
Another theory is that the island was formed by a rotational landslide.  Geologist Dave Petley of Durham University told Live Science that it's still too early to speculate but he said the low bow shape of the island could be an indicator that it was formed by a rotational landslide. Rotational landslides are characterized by the curved, concave shape formed in the earth after the slide, according to the USGS. Petley also observed that mud volcanoes typically spew wet mud. Photos of the island showed dry, rocky terrain.