In the described scenario we have a destruction of an ecosystem because of natural causes, volcano in this case. All that has left after the volcanic eruption has been barren land. After this has happened life started colonizing the volcanic island again, in a process known as primary succession. In the primary succession it is the organisms that have the lowest of requirements for survival that will inhabit the island. Over time, as they die, they will provide biomass for the ground, thus soil will start to form. Once there's soil formed a process called secondary succession will start. In this process the island will start to be inhabited by some plants and smaller animals. These plants and animals will contribute to further enhancing the living conditions on the island, and the island will gradually be getting larger plants and larger animals, thus a new ecosystem will be formed on the place of the old one.
In an ultramafic magma, there is concentration of Fe, Mg and Ca in the melt. An ultramafic magma is one with less amount of silica content. Ultramafic magma are usually rich in iron bearing minerals, magnesium and calcium. These minerals are usually the first to crystallize out in a melt when rocks are heated.
Carbonate ooze covers almost half of the world's seas floor. It is a calcium carbonate mud formed from that hard parts of free floating organisms in the river body. They are present above depth of 4500 meters. So at a water depth of 2500 meters, the sediments would most likely contain carbonate ooze. They are predominant in the deep Atlantic seafloor.
