Day 16: Unexpected discoveries
By Jamie Menzies
Sometimes, science doesn’t go exactly to plan.
This RV Investigator voyage now takes us to the Louisiade Plateau, which sits at the northern end of the Tasmantid chain of underwater volcanoes. The Louisiade Plateau is thought to represent the start of volcanism on the chain, representing the location where the hot, molten rock from the mantle hotspot first penetrated through the crust and erupted.
One of the key questions of this voyage is to determine if the Louisiade Plateau is a large igneous province, or LIP. LIPs are extremely large accumulations of igneous rocks, which are formed when magma, or melted rock, is cooled. So far we have found lots of igneous rocks like basalts formed from the cooling of lava from underwater volcanoes.
Image 1: A map of the world’s continental Large Igneous Provinces (LIPs).
If the Louisiade Plateau is a LIP, we would expect to find lots of igneous rocks that are roughly the same geologic age (i.e. erupted within a few million years of each other). The scientists expect that there will also be flood basalts – which are layers of basalt rock many kilometres wide and thick – representing a huge outpouring of lava. There are examples of flood basalts in LIPs such as the Siberian Traps in Russia and the Deccan Traps in India.
Image 2: The Deccan Traps in India have huge flood basalt deposits. In this photograph you can clearly see the thick layers of basalt.
When sampling the western edge of the Louisiade Plateau we found lots of basalt and other types of igneous rock, which will be analysed and “dated” (using chemistry to determine their age). We then commenced our transit to the north eastern side of the plateau, towards the Solomon Islands. The scientists like to call this Transiting With Optimistic Dredging (or TWODding…).
Image 3: The “lumps” on the ground spotted thanks to the RV Investigator’s multibeam SONAR.
We expected the top of the plateau to be relatively flat and not particularly geologically interesting, however, when watching the multibeam SONAR results come through, the scientists spotted some lumps on the seafloor that looked suspiciously like volcanoes…
Since we were feeling optimistic, the scientists decided to opportunistically dredge these mounds, and retrieved some lovely volcaniclastic rocks, definitely formed by volcanic activity.
Sometimes, science doesn’t always go as planned, but that doesn’t always mean bad results!