Below our ship the ocean floor is moving, two massive plates of Earth’s crust pushed apart in opposite directions to make way for new. We are sampling over the East Pacific Rise, one of many active spreading centers in the world’s oceans. The Earth’s crust is broken into a series of plates that are very slowly but surely in constant motion (the East Pacific Rise is considered a fast spreading center moving a whopping 7.5 cm each year). Between adjacent plates there are two types of boundaries, convergent and divergent. At convergent boundaries plates are being pushed together and one is subducted or forced beneath the other, sometimes causing earthquakes. Divergent plate boundaries, like the East Pacific Rise, are found where adjacent plates are being pushed apart, making way for new material. Molten hot magma from the Earth’s mantle is pushed up at these boundaries cooling to form new basaltic crust.
Hydrothermal vents form at divergent boundaries as cool surrounding seawater is pulled into the hot spreading center. As the water is heated it draws minerals and metals from Earth’s crust, spewing out a hot mixture of chemicals, gases and particles. Plumes of hydrothermal water cool and are carried away with currents, losing heat but maintaining high concentrations of metals and gases. Over the past few days we have been sampling plumes stemming from different vents along the rise. In the main lab, on-board analysts have been posting results showing high concentrations of magnesium, aluminum, mercury, and iron in two separate plumes found at different depths. As we move westward over the next week we will continue to look for elevated metal concentrations to determine the widespread influence of these plumes and how they affect metal concentrations in the deep Pacific Ocean.