Localized volcanic activity immediately above a mantle plume Reference : Skinner B.J., S.C.Porter & J.Park (2004), DYNAMIC EARTH, 5thedition, Jon Wiley & Sons.

    A spring in which the water is 6-9° C (10-15° F) warmer than the mean annual air temperature of its locality. Reference: Tarbouk, E.J. & F.K. Lutgens, (2006), EARTH, 8th edition, Pearson Education International.

    The expression at the Earth's surface of a mantle plume, or column of hot, buoyant rock rising in the mantle beneath a lithospheric plate.

    A climate characterized by severe winters and mild to warm summers with adequate annual precipitation. Typically located over large continental areas in the Northern Hemisphere between about 40 and 70 latitude.

    A so called "comfort index", the humidex reading provides a value based on a combination of temperature and humidity which represents what the temperature would be expected to be if the air were dry. If you consider the effect of evaporative cooling.... then in dry air at any given temperature you would not feel so warm as in moist air at the same temperature simply because your body could not cool down as quickly due to the reduced evaporative cooling.... Extremes of temperature and high humidity can cause health concerns in some people as a result.

    Generally, a measure of the water vapor content of the air. Popularly, it is used synonymously with relative humidity See relative humidity.

    An index that relates air temperature and relative humidity to how hot it feels.

    Organic matter in soil produced by the decomposition of plants and animals. Reference: Tarbouk, E.J. & F.K. Lutgens, (2006), EARTH, 8th edition, Pearson Education International.

    (also known as Typhoon, Tropical Cyclones, Willy-Willies) Tropical storms with wind speeds of 64 knots (117 km/h) up to 240 knots (414 km/h) that can be thousands of square kilometers in size. Such systems usually have a lifespan of several days. In the North Atlantic, the hurricane season is from May to November, but the majority of storms occur in August, September and October. A hurricane warnng is issued if winds are expected to exceed 64 knots (117 km/h).

    A warning given when it is likely that a hurricane will strike an area within 24 hours.