Tumuli (tumulus, singular) Also called pressure ridges, tumuli are characterized
by domed shape structures due to the channeling of large lava flows along a
gentle slope. A tumulus represents a small-sized volcanic dome where the
doming and bursting of the chilled crust occurs during the flowing of hot lava in
a conduit. A single and homogeneous type of flow will form a tumulus. The
bursting and cracking of the convex shaped portion is the result of pressure
differences between the gaseous phases in the hot conduit and the exterior
Ultramafic Dark-green colored intrusive rocks composed of ferromagnesian
minerals. As opposed to mafic extrusives and intrusives. No ultramafic rock are
extruded, but they are only intruded into the lithosphere where they may later
be uplifted due to tectonic activities
Vesicles Holes or pockmarks in solid rocks formed when gas (volatiles) escaped
from gas-filled cavities before the melt solidified
Volcaniclastics Fragmented deposits of explosive origin, including bombs, shards
and lapilli
Wilson Cycle Cycle of Continent-Ocean plate motions so-called in honor of Tuzo
Wilson who first hypothesized the existence of several stages of opening and
closing of the oceanic basins due to ‘‘continental drift’’
Xenolith and xenocryst Foreign rocks (xenolith) and mineral crystals (xenocryst)
included in another rock type such as basalt, dolerite, gabbro or peridotite.
Their importance resides in the fact that they represent solids that were torn-off
from an outcrop and remobilized during magma circulation in the lithosphere
therefore they can provide information on the composition of the substratum.
They are recognized by their chilled contour lines due to reaction with the host
rock, giving rise to corroded edges and chemical disequilibrium with their host
rock
Zeolite Group of minerals including natrolite (hydrated sodium aluminum silicate) and heulandite (hydrated calcium aluminum silicate). They are a colorless
or white water-enriched (hydrous) aluminum silicate that contains calcium,
sodium and potassium. They are known to form crystals in the cavities of rocks
such as geodes
370
Glossary
by domed shape structures due to the channeling of large lava flows along a
gentle slope. A tumulus represents a small-sized volcanic dome where the
doming and bursting of the chilled crust occurs during the flowing of hot lava in
a conduit. A single and homogeneous type of flow will form a tumulus. The
bursting and cracking of the convex shaped portion is the result of pressure
differences between the gaseous phases in the hot conduit and the exterior
Ultramafic Dark-green colored intrusive rocks composed of ferromagnesian
minerals. As opposed to mafic extrusives and intrusives. No ultramafic rock are
extruded, but they are only intruded into the lithosphere where they may later
be uplifted due to tectonic activities
Vesicles Holes or pockmarks in solid rocks formed when gas (volatiles) escaped
from gas-filled cavities before the melt solidified
Volcaniclastics Fragmented deposits of explosive origin, including bombs, shards
and lapilli
Wilson Cycle Cycle of Continent-Ocean plate motions so-called in honor of Tuzo
Wilson who first hypothesized the existence of several stages of opening and
closing of the oceanic basins due to ‘‘continental drift’’
Xenolith and xenocryst Foreign rocks (xenolith) and mineral crystals (xenocryst)
included in another rock type such as basalt, dolerite, gabbro or peridotite.
Their importance resides in the fact that they represent solids that were torn-off
from an outcrop and remobilized during magma circulation in the lithosphere
therefore they can provide information on the composition of the substratum.
They are recognized by their chilled contour lines due to reaction with the host
rock, giving rise to corroded edges and chemical disequilibrium with their host
rock
Zeolite Group of minerals including natrolite (hydrated sodium aluminum silicate) and heulandite (hydrated calcium aluminum silicate). They are a colorless
or white water-enriched (hydrous) aluminum silicate that contains calcium,
sodium and potassium. They are known to form crystals in the cavities of rocks
such as geodes
370
Glossary
Précédent