| HABITAT | The immediate surroundings of a plant or animal, with everything necessary to sustain life. Biology - Flora & Fauna. Ref AC |
| HALF BLIND VALLEY | A blind valley that overflows its threshold when the flow exceeds a certain limit, beyond which the stream sink cannot accept all the water Karst - Depression Features of. Ref JJ |
| HALF TUBE | Exposed on a fractured rock surface. Often meandering or 'anastomosing'. see Anastomosis. Speleology term. Ref JJ |
| HALITE | The common salt sodium chloride NaCl as a mineral in the cubic crystalline system. May form as decorations on dry caves as, dripstone, crust, flowstone, stalactite, stalagmite and other forms. Mineral, Rock and Chemical terms. Ref JJ |
| HALL | A lofty chamber that is longer than it is wide. Cave - Parts of. Ref JJ |
| HARNESS | In climbing, an arrangement of tape, either the seat harness or chest harness for the attachment of ascenders or descenders. Climbing and SRT. Ref JJ |
| HELICTITE | A speleothem, appearing to defy gravity, being a curved or angular twiglike lareral projection of calcim carbonate. Has a tiny central canal. See Anthodite. Cave - Depositional Features. Ref JJ |
| HELIGMITE | A helictite that grows on a cave floor or a shelf. Usually thin, curved and angular. Cave - Depositional Features. Ref WM |
| HELMET | A miners, climbers or other kind of non metallic protective helmet used in caving. Australia does not have a standard for caving helmets. A chin strap is recommended for vertical work. A sun visor is generally an inconvenience. Speleology term. Ref JJ |
| HERBIVORE | An animal that eats plants. Fauna. Ref MM |
| HISTOPLASMOSIS | A lung disease usually mild in effect but known to be fatal. May be caught from guano in caves, caused by fungus, Histoplasmosis capsulatum. Miscellaneous terms. Ref JJ |
| HOLOKARST | Having bare surfaces on thick deposits of limestone that extend below sea level and little or no surface drainage. They have karren, dolines, uvalas and cave systems. cf merokarst. Karst - Kinds of. Ref WM |
| HORIZONTAL ANGLE | The difference in direction of two survey lines measured clockwise in a horizontal plane. Survey & Mapping term. Ref JJ |
| HORNITO | A small spatter cone up to 5 m high which spits out red hot drops of lava. Lava Cave term. Ref KG |
| HUMIDITY, RELATIVE | The ratio of the amount of water present in air to the amount present at saturation. Most caves have high humidity because climatic conditions tend to be constant with very little evaporative moisture loss. But caves can have low humidity. Speleology term. Ref MM |
| HYDROSTATIC PRESSURE | The pressure due to a column of water. Speleology term. Ref JJ |
| HYPOGEAN | Pertaining to the domain below the endogean, including the dark zone of caves. cf Epigean, Endogean. Speleology term. Ref JJ |
| HYPORHEOS | Pertaining to water flowing over streambeds. cf Lotic. Speleology term. Ref AC |