Descriptionary

nerve the principal vein of a leaf.

orchard a cultivated stand of fruit or nut trees.

phloem the spongy layer of inner bark.

pitch pocket a concentration or pocket of resin in the wood of a conifer.

pollard a tree with its top cut to stimulate new root growth.

prop roots roots that curve out from a trunk above ground, giving the appearance of stilts, and com­monly found in jungle areas where root systems are shallow.

rain forest a thick, tropical, mostly evergreen forest that receives at least 100 inches of rain per year.

ramose having many branches.

resin secretions, hard or liquid, from small cham­bers or passages within a tree.

sapling a young tree approximately 2 to 4 inches around.

sapwood the wood between the bark and the heart- wood, paler and lighter than heartwood.

scrub any collection of low trees and shrubs.

second growth growth that replaces that removed by cutting or by fire.

scurf flaky bark, as a birch.

shelterbelt in a field, a strip of trees or shrubs pro­viding shelter from the elements.

stand any close grouping or line of trees.

stoma a breathing pore of a leaf.

strangler a jungle plant (fig or banyan) starting life as a vine on the branch of a host tree, then working its way down to ground level to root; in time it grows woodier and thicker and may fully encompass the host tree, sometimes killing it.

sunscald localized injury to bark or cambium caused by high heat and sunlight.

sylva collective term for the forest trees of a region.

taiga subarctic coniferous forests consisting of small trees.

taproot the first and strongest central root of a tree, usually growing straight down.

thicket dense underbrush.

topiary trees or shrubs sculpted into fantastic shapes through pruning.

virgin forest a forest untouched by humans.

weald British term for a woodland.

windbreak a line or grouping of trees planted to act as a brake against the wind's erosive action, especially around a farm.

windfall branches and leaves knocked off by the wind.

windthrow trees knocked over by the wind.

valleys

dale a broad, open valley, especially those found in England and Scotland.

dell a small, forested valley.

drowned valley a valley that has been submerged under water.

glen long, narrow, steep-sided valley, usually having a river or stream in the bottom.

rift valley land that has sunk between two faults, forming a long, relatively narrow valley.

vale a valley, usually with a river.

volcanoes

aa Hawaiian term for a rough, crumbly type of hardened lava.

accretionary lava ball: a semi-solidified glob of lava, from fist-size to boulder-size, on a river of lava or on the slope of a cinder cone.

active volcano a volcano that is either erupting cur­rently or that has erupted within recorded history and will probably erupt again.

andesite a darkish volcanic rock comprised of silica, iron, and magnesium.

ash tiny particles of pulverized rock blown out of a volcano.

ashfall an accumulation of ash that has fallen out from an eruption.

basalt a dark, igneous rock produced by volcanoes.

basal wreck the truncated cone left after the erup­tion and collapse of a volcano.

base surge the explosive reaction of lava when it meets with water.

blister a hollow bubble or doming of a crust of lava, usually about one meter in diameter, formed by hot gas.

block any block-shaped rock ejected in an eruption.

blowhole a secondary crater or vent through which hot gas is discharged.

bomb a solidified blob of molten rock ejected from a volcano.

caldera a large crater formed by a volcanic erup­tion, often evolving into a lake.

cataclysm any violent upheaval, inundation, or deluge.

cinder cone a conelike mound formed by escaping volcanic gas and ash.

clastic of any ejaculate, broken or fragmented; sand is a clastic material.

composite volcano a volcano having more than one major vent. Also, any volcano with a vent and a dome.

compression waves seismic ground movement sim­ilar to the movement of a slinky toy.

conduit any natural cavity or passage through which magma flows.

continental drift the natural movement or migra­tion of continents toward or away from one another, responsible for volcanic activity worldwide.

VOLCANOES 159 crater the mouth of a volcano.

curtain of fire one or more lava fountains spewing from a long fissure and resembling a curtain.

dacite a light-colored volcanic rock comprised of silica, sodium, and potassium.

debris avalanche a sudden slippage and flow of a mass of rocks, water, snow, mud, trees, or other debris down a slope.

detachment plane in an avalanche or landslide, the surface from which a mass disengages itself.