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Macro-invertebrate
Small creature living in the seabed and subsoil, like earthworms, snails and beetles.

Madrid Protocol
A protocol to the 11th Antarctic Treaty to provide for Antarctica’s environmental protection.

Mafic
Term used for silicate minerals, magmas and rocks, which are relatively high in the heavier elements.

Magmatic activity
The flow of magma (lava).

Marginal cost
Additional cost that arises from the expansion of activity. For example, emission reduction by one additional unit.

Maturation
The geological process of changing with time. For example, the alteration of peat into lignite, then into sub-bituminous and bituminous coal, and then into anthracite.

Mature sedimentary basins
Geological provinces formed by the deposition of particulate matter under water when the deposits have matured into hydrocarbon reserves.

MEA
Mono-ethanolamine.

Medium-gravity oil
Oil with a density of between about 850 and 925kg/m3 (between 20 and 30 API).

Membrane
A sheet or block of material that selectively separates the components of a fluid mixture.

Metamorphic
Of rocks that have been altered by heat or pressure.

Mica
Class of silicate minerals with internal plate structure.

Microseismicity
Small-scale seismic tremors.

Migration
The movement of fluids in reservoir rocks.

Mineral trapa
A geological structure in which fluids are retained by the reaction of the fluid to form a stable mineral.

Miscible displacement
Injection process that introduces miscible gases into the reservoir, thereby maintaining reservoir pressure and improving oil displacement.

Mitigation
The process of reducing the impact of any failure.

Monitoring
The process of measuring the quantity of carbon dioxide stored and its location.

Monte Carlo
A modelling technique in which the statistical properties of outcomes are tested by random inputs.

Mudstone
A very fine-grained sedimentary rock formed from mud.

MWh
Megawatt-hour.