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Clouds form when air that is warm and moist cools and expands. Clouds are just tiny droplets of water in the atmosphere. As you can see from the image below, the air cools as it rises, but cool air is able to hold less water than warm air. Thus, this excess water in the cool air condenses, and when enough of it does so, a cloud is formed.
Clouds are formed by way of four processes : 1) surface heating, 2) mountains and terrains, 3) air masses that are forced to rise and cool, and 4) cold or warm weather fronts.
1) The first process is perhaps the simplest: the sun heats the earth and thus the air, this warm air rises, expands, and cools, forming clouds like in the image above.
2) Clouds are also formed when air encounters mountains or other topography. The air rises and cools and, again, the air cannot hold all of the water it held when warm so clouds form.
3) The air is also forced to rise when wind in a low pressure system forces the air to rise up. Related to number 2, if air is forced to rise because of topography that slopes upwards, clouds may also form.
4) Finally, weather fronts cause cloud formation. Specifically, warm fronts create clouds because the warm air rises above the cold air and cold fronts create clouds because the cold air displaces or moves the warm air up.
To conclude, many factors affect cloud formation, including topography, air temperature, and humidity.
Here's a very comprehensive link on cloud formation if you're looking for more.
Additionally, clouds can form in areas where precipitation has been ongoing or particularly heavy. The falling precipitation brings moisture lower down in the atmosphere, and we get a ragged layer (either stratus or stratus fractus) form, usually within 1,500 ft of the ground or lower.
Finally, since Fog is cloud at the surface of the Earth, in areas where fog has formed, surface winds can lift the fog, once it is aloft it becomes a cloud layer (stratus).
Multiple things, depending on the context of the question.
Personally, I define gneiss as a foliated metamorphic rock that most commonly is formed from shale (through a series of other transformations), as a result of regional metamorphism (formed under a lot of pressure and heat, over a fairly large area). Additionally, it usually has a banded appearance, which isn't unique among metamorphic rocks, but it does help it separate it from the non-banded rocks.
Most people can't legitimately say that gneiss can be defined by its composition, because it varies, but most gneiss samples will have bands of quarts (silicon dioxide) and feldspar (silica and aluminum containing). As a result, I don't primarily define gneiss from its chemistry.
Sometimes it's nice to see it compared to other rocks to help choose your own path to its definition. Below is an ID chart used to determine the rock type of some popular metamorphic rocks.
Here are some different gneiss rock samples, just to show you the variation:
Snowball Earth refers to the theory stating that, at multiple times, the entire surface of the planet was frozen. This theory has important implications for any existing life during those periods.
In brief, Snowball Earth is a theory stating that the entire planet was frozen, it may have occurred multiple times between 850-635 mya, and it would have made for very challenging living conditions for any organisms. Following Snowball Earth is the Cambrian Explosion.
Snowball Earth refers to the theory stating that, possibly at multiple periods in times, the entire surface of the planet was frozen. This includes both land surfaces but also oceans. Scientists have not agreed on what exactly caused Snowball Earth. It is likely that low levels of carbon dioxide in the atmosphere were at least partially responsible for cooling the planet.
These episodes are thought to have happened between 850-635 million years ago (mya), during the Cryogenian period.
With everything frozen, biological, geological, and chemical processes were disrupted, such as the carbon cycle and the rock cycle. Carbon dioxide was no longer being removed from the atmosphere and gradually levels increased until they were high enough to cause a greenhouse effect. Volcanic eruptions under the ocean may have sped this process along by adding more greenhouse gases to the atmosphere (see here).
Following Snowball Earth was a period of great change in the composition of the atmosphere. We see oxygen levels reach their current numbers. After this increase in atmospheric oxygen, the Cambrian Explosion occurred, and this is when we see a substantial number of multicellular organisms evolve.
Conditions made it very challenging for life to survive Snowball Earth. Life may have survived in small, unfrozen areas of the ocean (see here). There may also have been breaks of time where the entire world was not frozen, allowing microbial organisms to survive (see here).
Relative humidity is affected by temperature and the amount of moisture or water vapor in the surrounding atmosphere.
Hot or warm air can "dissolve" more water vapor than cold air. When warm air with a high water content is cooled the relative humidity increases. This is because the percentage ( relative humidity) of water vapor increases as the carrying capacity of the air decreases with no loss of water vapor.
Air over an ocean usually has a high water vapor content because of evaporation. This air, when it moves over the colder land mass will cool from contact with the ground. It will also cool if it rises in the atmosphere, as the atmosphere pressure drops as you go higher (simply because there is less atmosphere above you). The Gay Lussac law states pressure and temperature are proportionate (as one drops so does the other). The cooler air has less ability to hold water vapor in solution. If the air cools enough the amount of vapor in the air will reach the point where it is the same as the maximum amount of vapor the air can hold. This will result in the water vapor condensing, resulting in cloud formation.
If the temperature of the air remains the same the relative humidity can be affected by adding water vapor. If a sample of air is holding half of the total amount of water vapor it can hold, and we add more water vapor, the relative humidity will start at 50% and then increase.
The vertical on this chart is the actual mass of the water in the air (called absolute humidity or mixing ratio). The horizontal is the air temperature. The red curve indicates at what temperature the absolute humidity is at the maximum (100 percent relative humidity). You can see that if you start with a given absolute humidity (say 20g/kg of air), at 35 Celsius it is holding about half the vapor it can. If that air cools to 25 Celsius, it is now at 100 % relative humidity.
The East Coast of North America is a passive tectonic margin; whereas, the West Coast is an active margin.
The East Coast is currently a passive margin where the North American Plate is moving slowly away from the European Plate. On the West Coast however, several plates are interacting to cause frequent earthquakes and volcanism. In California, The North American Plate and Pacific Plate are moving past each other along a transform margin (the San Andreas Fault System).
In the Pacific Northwest, the Juan de Fuca Plate is being subducted beneath the North American Plate at the Cascadia subduction zone. (See below) The result is the string of active volcanoes (the Cascades) that extends from Northern California to southern Canada, including Mt. St. Helens and Mt. Ranier.
I am not sure of what you mean by "ridge push"
The formation of oceans is generally related to a process named "rifting" or "rift valley formation". A spectacular example is evident in East Africa where a huge fault is running from North to South through the Red Sea and the Lake Region
Rifts open up because of the separation of tectonic plates and the
valley is invaded by waters that eventually may grow as large as the Atlantic Ocean.
The simplified rifting mechanism is explained in the followin image
The slow building of a mountain chain in the middle of the rift valley is not the cause, but the consequence of the rifting process.
The actual motor of the process is the convective motion within the Mantle that pushes apart the two continental plates on the down trend while accumulating matter in the middle in the up trend.
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