P-T

Peak Ground Acceleration
A short-period ground motion parameter that is proportional to force. It is the most commonly mapped ground motion parameter because current building codes include seismic provisions which specify the horizontal force a building should be able to withstand during an earthquake.

Pelagic
Of, relating to, or living in open oceans or seas.

Photosynthesis
The process by which green plants, algae, diatoms, and certain forms of bacteria make carbohydrates from carbon dioxide and water in the presence of chlorophyll; using energy captured from sunlight by chlorophyll, and releasing excess oxygen as a byproduct.

Phyllogenetic
The relationships between taxa (species, genus, family, etc.) on the basis of gene sequences.

Phytoplankton
The photosynthesizing organisms residing in the plankton.

Plankton
Organisms living suspended in the water column and incapable of moving against water currents.

Plates
The rigid pieces that make up the puzzle of the Earth's crust.

Plume
A visible or measurable discharge from a given point of origin. Plumes can be a visible particulate, or thermal, and occur in water or air.

Porphyry
A variety of igneous rock consisting of large-grained crystals, such as feldspar or quartz, dispersed in a fine-grained matrix or groundmass. Porphyry deposits are formed when a column of rising magma is cooled in two stages. This process is one of the main reasons for the existence of rich, localized metal ore deposits such as those of gold, copper, molybdenum, lead, tin, zinc and tungsten.

Precipitation
Related to hydrothermal fluids, the process of separating a solid from a solution. Metal sulphides are precipitated from hydrothermal fluid on the seafloor.

ROV
Remotely operated underwater vehicles, usually tethered, unoccupied and operated by a person aboard a vessel.

Sedimentation
Solids settling out of a liquid by gravity.

SMS Deposit
Seafloor Massive Sulphide deposits are formed when water is driven through permeable ocean crust as a result of thermal convection caused by hot magma at depth. Hot metal–bearing hydrothermal fluids with temperatures in excess of 200°C mix with cold sea water with temperatures of 2°C – 4°C, resulting in precipitation of metal-bearing sulphide minerals on the seafloor.
 
Species Richness
The number of different species in an area.

Spreading
The separation of plates such as the spreading that occurs along mid-ocean ridges.

Spring Tide
The phase of the tidal cycle when tidal range is at a maximum.

Spud
Moveable anchor points allowing the Seafloor Mining Tool to walk over the seafloor.

Stratovolcano
A stratovolcano, also called a composite volcano, is a tall, conical volcano composed of many layers of hardened lava, tephra, and volcanic ash.  These volcanoes are characterized by a steep profile and periodic, explosive eruptions.  The lava that flows from them is viscous, and cools and hardens before spreading very far.  The source magma of this rock is classified as acidic, having high to intermediate levels of silica (as in rhyolite, dacite, or andesite).  This is in contrast to less viscous basic magma that forms shield volcanoes (such as Mauna Loa in Hawaii), which have a wide base and more gently sloping profiles.

Subduction
The process by which one tectonic plate moves beneath another.

Submersible
Equipment designed to operate beneath the ocean surface. Deep-sea submersibles are designed to go to depths greater than ordinary submarines (depths greater than 2,000 metres) and are typically remotely-operated.

Sulfides
Sulfur-bearing minerals.

Symbionts
Microorganisms that live on or within the cells of host animals, with both deriving mutual benefit.

Taxa
Classification of organisms into groups (taxa) according to similarity.

Topography
Variation in altitude of the landscape. 

Tsunami
An ocean wave generated by a submarine earthquake, volcano or landslide. (Also known as a seismic sea wave, and incorrectly as a tidal wave).