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The first reason is it is if you know the wind speed and direction you will know what direction the weather is coming from and how fast it is moving. For example, if it is raining at a town 80 nautical miles (wind is measured in knots official) to the west of a second town, and the radar returns show that the precipitation is moving to the east at a speed of 20 kts, a relatively accurate prediction for the second town is that in 4 hours time it will be raining.
More importantly, wind direction and speed helps to plot the atmospheric pressure. The Buy Ballot law states that in the Northern Hemisphere, if the wind is at your back the area of low pressure is to your left. When you plot many wind points you get a pattern that illustrates the pressure pattern and when you look at speed you get an idea how far away the location is from the center of the pressure center.
This map shows how plotting the wind can show you the location of the pressure center. The thing to remember is that sometimes measuring stations are more than 100 miles apart, so plotting the wind like this can really help.
Stratigraphy and its fundamental laws.
Bear in mind that when geologists began dating the Earth's layers the accepted time scale was only a few thousand years long.
The Earth had been created by God and the time of origin had been fixed, estimating the life span of the Patriarchs, to approximately 6300 years.
It is only by the early 19th century that this view begins to be contested. It is only after the works of Cavendish, Buffon or Darwin that the very notion of a million years begins to take shape.
Thusfar the relative time scales that could be established locally using the basic laws of stratigraphy (cross-cutting, superposition, horizontality...) were sufficient to resolve a local problem and build a local structural model.
It was when palaeontology understood that what was true here was also true at the other end of the planet that geologists started extending their time lines and correlating identical or similar events across the world.
When they began doing that, a wealth of information had been already collected locally, and it was therefore a matter of piling it all up checking similarities and identities.
The exercise was followed by the hunt for major worldwide events that could be recognisable everywhere. These turned out to be marine transgressions or regressions, the appearance or disappearance of certain life species, and volcanic or astronomical event such as the Iridium level K-Pg delimiting the Cretaceous across the world.
Once the stratigraphic pile was built and accepted, it was a matter of devising a time scale.
No one believed in those 6000 year anymore (not even the clerics). Evaluation of the age of the Earth on the basis of thermal and depositional models had brought that limit to 75,000 to 600,000 and even to a million years. Simply by looking at the tides on a beach anyone could see that it would take a long time to build a carbonate strata.
A pile of several hundred metres of limestones had to be equivalent to that long time multiplied by the number of strata one could fit in several hundred metres. The results were staggering. The million year could not be the time limit, it had to be the time unit.
In the meantime astronomy had made huge progresses. The velocity of light having been estimated, the size of the Universe was being calculated in terms of millions and millions of kilometres. The Earth had to be part of that game. Playing with a similar deck of cards.
Radiometry was then introduced giving precise results for volcanic rocks. Evolution gave an idea of the time needed for genetic mutations… little by little approximate time scales were devised to fit the general picture and the correlation between all of them and the advent of more and more information produced better and better time models.
But models they still were. The one we have today, is the result of astrophysical measurements, extrapolations of plate tectonics displacements and paleontological data.
It could be argued that our modern geological time scale, with its few fixed radiometric points, is still only a relative one. To make it absolute one would have to fix a universally accepted starting point. The origin of the coordinate axes. An antecedent that, at the present time, geoscientists are not prepared to accept.
I believe you are referring to Hadley cells.
The diagram above shows all the circulation cells of the atmosphere, and you can see the ones just north and south of the Equator are called Hadley cells (named after George Hadley who first describe the mechanisms for trade winds).
At the equator the high amount of solar energy heats the atmosphere. There is a lot of moisture at the equator (there is a lot of ocean at the equator), and that adds water vapor to the atmosphere. Water vapor has a lower weight than nitrogen (the primary component of the atmosphere) and that lowers the weight of the atmosphere and therefore the pressure. Furthermore, as the air is heated it expands and that lowers the density causing upward motion of air. End result the air is rising.
As the pressure decreases with height the temperature decreases as well. This lowers the amount of water vapor the air can hold and cause precipitation. This is important later.
With lower pressure at the equator, the pressure gradient force (force causing air to move from areas of high pressure to areas of low pressure) brings air to the Intertropical Convergence Zone (named due to the incoming air converging). End result of this is surface winds move air toward the equator.
With air converging and rising at the equator, when it reaches the tropopause (top of the troposphere) it is forced to move outward away from the equator. As it moves further away, and as has further precipitation the weight of the air increases. This causes descending motion of air at around 30 degrees latitude. This air, as it descends also warms from the increase in pressure. This further dries out the air and increases pressure. This is why if you look around the globe you will see a lot of deserts at around 30 degrees latitude.
As you can see from the global diagram above this closes the system, giving you your Hadley cell.
The earth goes through alternating periods of global warming and cooling.
What causes these alternations of climate is not completely known.
The solar flares and storms affect the climate. Volcanic eruptions can cause major cooling periods. Increased glaciers reflect more light causing a spiral effect of global cooling.
There is substantial evidence of a global ice age where glaciers covered large areas of the earth, and people retreated to living in caves.
Around 1000- 1200 AD there was a warming trend. Vikings grew grapes in Greenland which was green at the time. The Vikings sailed across the arctic sea in the mythical Northwest passage, between North America and Russia. (Rus was a name for the north people and Russia is named after these Vikings.)
Even further back the age of the Dinosaurs was much warmer throughout the globe. Vast coal deposits are evidence of lush vegatation. Greater humidity and cloud cover are thought to be responsible for the jungle like climate of this era.
Climate naturally goes through alternating periods of warming and cooling. Lush tropical climates are followed by ice ages. What causes these fluctuations is not fully understood.
The windward side of a mountain is the side in which moisture in the air is released as it goes up in elevation, and the leeward side is the side where the air goes down into the land, now dry.
The best way to explain windward and leeward is an example. An example close to where I live is Mount Hood, Oregon. The Pacific Ocean is west of Mount Hood, and all air heading towards the east picks up moisture from the ocean. As the most air travels throughout the land, it rains so the area on the windward side of a mountain has more precipitation.
When the moist air heads towards the mountain (Mount Hood in this case), it gains elevation. Air pressure is the weight of the atmosphere, so as the air moves up there is less atmosphere above it and therefore less pressure. According to Gay Lussac's law pressure and temperature are proportional, so as the pressure drops the temperature also drops. The amount of water vapor air can hold is based on it's temperature, the cooler the air the less vapor. So as the air cools condensation occurs and precipitates out.
The red line in the graph above shows the maximum amount of water vapor air can hold, and you can see it increases with temperature.
The side of the mountain where this happens is called the windward side, since this is the side the wind blows against. When the air travels over the mountain and descends that's called the leeward side.
On the leeward side, as the air loses elevation the pressure increases, and therefore the temperature increase. As the graph above shows as the air warms it's ability to hold moisture increases, but since the air lost moisture on the windward side, if there is no source for new moisture on the leeward side the air just gets drier and drier. The leeward area is often a desert or a dry place, since the air has much less moisture than it can actually hold.
Here's a map of Oregon to show an example:
The green area is the area west of the mountain, so the west side of the mountains is the windward area (Also Mount Hood is part of the Cascade Mountains). The orange area is then the desert area, and then that means the east side of the mountains is the leeward side.
a) Fold mountains are pushed up into anticlines and synclines.
Here is a diagram of fold mountains
The section on the right is a diagram of upward foldings called anticlines.
Downward folding creates synclines.
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Here's another diagram showing the forces that crunch the earth's crust together so that it folds into mountains
Here's a photograph of fold mountains in Crete. It clearly shows the layers of the crust folded up into anticlines and down into synclines.
The European Alps are a famous example of a range of folded mountains.
Other examples of fold mountains are the Himalayas, the Rockies, and the Andes.
Fold mountains are the highest mountains on earth.
You can find out more about folded mountains here:
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