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Clouds
Cloud is a mass of tiny droplets of water or ice crystals formed by condensation at considerable elevations.Clouds are classified on the basis of height or on the basis of its structure,size shape etc..
On the basis of height clouds are classified into
- High level clouds:formed at an average height between 6 km to 12 km.They are generally prefixed the name “cirro”.eg: Cirrus, cirrostratus, cirrocumulus
- Medium level clouds:Average height fro 2000 to 6000 kms. Usually they are prefixed with the name “alto”.eg: altocumulus, altostratus
- Low level clouds:Found below 2 kms. Generally not given any prefixes eg: stratus, cumulus. nimbostratus
Based on structure some important cloud types are given below:
- Stratus:
- Uniformed layer clouds
- formed at a height less than 2 kms.
- are more known for drizzle than precipitation
- Formed in sheets and usually associated with overcast conditions
- Fog or mist are a result of stratus clouds
- Altostratus
- Appear in altitudes between 2 kms and 6 kms.
- Very thin and uniform
- Grey or blue grey thus creating overcast conditions.
- Translucent enough to see suns rays through it and do not make shadows on the surface of the earth.
- Usually associated with the coming of rains but incapable of rains by themselves
- Cumulus
- Formed at height less than 2 kms.
- Usually associated with fair weather but at times can cause short and heavy rainfall
- Most recognizable ouds
- Have flat bases and lumpy outlines
- Responsible for creation of cold fronts
- Formed by frontal lifting or convection
- Nimbostratus
- Formed below 2kms.
- Cause heavy precipitation
- Cumulonimbus
- Cause heavy thunderstorms
- Cirrus clouds
- Highest clouds in troposphere
- Temperature so cold that ice crystals are formed.
- indication of approaching bad weather
- Fastest moving in the atmosphere
- Cirrostratus clouds
- Halos around the sun and moon are due to these clouds
- Cirrocumulus
- This appears as white globular masses.forming ripples.
- Altocumulus
- Normally indicate fine weather
- Wooly,bumpy clouds arranged in layers
Tornadoes and tropical cyclones
Both tornadoes and tropical cyclones are rapidly rotating column of air formed around low pressure centers. But the similarity ends there. In fact,tornadoes and tropical cyclones are entirely different.
Tornadoes are extremely violent winds moving with seeds even greater than 300km/hr.But tropical cyclones are much slower just above 120km/hr.Tornadoes are smaller in size with diameter only few 100 meters in extent whereas tropical cyclones have diameter of a few 100kms.
Tornadoes usually originate over land mass when sharp wind shears are created at the frontal boundaries owing to sharp temperature differences.But tropical cyclones are usually formed over calm and warm oceanic waters where enough moisture presence is ensured.Moreover,tropical cyclones usually die out on making a landfall due to the absence of sufficient moisture content.In some instances tropical cyclones may provide conditions for the creation of tornadoes.
Further tornadoes so formed usually last only for a few hours but tropical cyclones may last for a few days.
Usually tornadoes are a common occurrence in the “tornado ally” in the central plains of the U.S.Tropical cyclones on the other hand are common occurrence in the Odisha coast of India
Diastrophism and Volcanism
Both Diastropism and volcanism are endogenic process but both are different in subtle ways.
Diastrophism
Diastrophism is a term referring to the large scale distortions on the earth’s crust.It involves process that create mountains,ocean basins etc..Also it involves folding,faulting uplift and depressions of the lithosphere.
Usually diastrophic processes include:(i) orogenic processes involving mountain building usually in tangential direction to the surface of earth (ii) epeirogenic processes involving broad uplift or depression of crust in a vertical or radial direction (iii)earthquakes involving local relatively minor movements (iv) plate tectonics involving horizontal movements of crustal planes.
Volcanism
Usually diastrophism deals with movement of solid crust material but volcanism usually includes movement of molten magma onto the surface of the earth.The process of volcanism is associated with the formation of many intrusive and extrusive land formations.
Role in evolution of earth
Both diastrophism and volcanism has contributed to the evolution of earth as we see it today.Diastrophism includes tectonics and plate tectonics,which have been reesponsible for the disintegration pangea and the resultant movement and drifting of the plates to reach today’s postion.Faulting and folding is responsible for many regional landmass modification including creation and destruction.Himalayan orogeny is a as result of massive folding.
Volcanism too has played a huge role in the evolutionary process.Volcanic eruption from the oceanic ridges have resulted in creation of many landmasses and island arcs.For eg, japanese island arc,Hawiian islands fall in this category.Volcanic eruption result in many other endogenic and exogenic landforms like batholiths,lacoliths,caldera etc..
Hence both diastrophism and volcanism have played a crucial role in shaping the earth as wee see today.
neogeographia 