Geography Concepts

At sea, ITCZ area is called doldrums because sailors in olden days used to get becalmed here.
It’s the region of weak winds (small pressure gradients), High Humidity and High Temperatures occuring heat near equator.

Horse Latitude:-
In olden days, Zones at about 30 N/S Degree were known as Horse latitude.
When ships were becalmed, horses were thrown to reduce the load.
Here, the air is comparatively dry and winds are calm and light, because of small pressure gradient force.
It’s the region of descending air currents or wind divergent ie. Anti-Cyclonic condition.

Trade Winds:-
Trade winds are most regular of all the planetary winds and in general they blow with great force and in constant direction.

Since trade winds blow from the subtropical latitudes to the warmer equatorial latitudes, they have great capacity of holding moisture.

In their passage across oceans, they gather more moisture and bring heavy rainfall to the east coast of continents.

As their offshore on the west coast, these regions suffer from great aridity and form hot deserts of the world.
E.g. Sahara, Kalahari, Atacama, Great Australian deserts.

Interior area of Australia
The term outback in Australia refers to dry interior region.
Term outback implies “Never Never” ( Never Never go there)

Westerlies are much less ( constant and persistent) than trade winds.

Seismic Gap:-
It’s the earthquake prone area where occurs a gap in the occurrence record of major earthquakes.
This means, that statistically, major earthquake is due ie, much more time had elapsed since the last major earthquake than the average time gap between two major earthquake as per the historical occurances.

Earthquake waves gets significantly amplified when they passed through soft grounded ( water saturated alluvial deposits).
Liquefaction is sudden loss of strength of water saturated soils resulting from shaking during an earthquake.
It can cause large ground cracks to open, shaking can cause soils to consolidate and thus to occupy a smaller volume.
During shaking of an earthquake, the water saturated material may result in subsidence, fracturing and horizontal sliding of the ground surface.