# Make the internet a better place to learn

## How are clouds formed and what factors affect their formation?

Kate M.
3 years ago

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).

## What are the major layers of the earth?

Sam S.
2 years ago

There are four major layers.

#### Explanation:

They are...

The Crust:

• Very thin
• The part you live on top of

• Separated into plates (when they knock against each other Earthquakes happen.)

The Mantle:

• The largest layer (1800 miles thick)

• Flows because of very high temperatures

• The movement of the plates is caused by this flowing

The Outer Core:

• Composed of the metals Nickel and Iron

• Completely liquid because of extremely high temperatures (4000-9000 degrees Fahrenheit)

The Inner Core:

• Temperatures and pressures are so high that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place as a solid.

Note that some of these layers can be broken down and described further.

## When the time of day for a certain ship at sea is 12 noon, the time of day at the prime meridian (0° longitude) is 5 P.M. What is the ship’s longitude?

Stefan V.
2 years ago

${75}^{\circ} \text{W}$

#### Explanation:

The trick with this problem is to figure out the position of the ship in relation to the Prime Meridian, that is, on which side of the Prime Meridian, East or West, you can expect to find the ship.

As you know, longitude expresses the position of a point on Earth's surface in terms of how many degrees East or West relative to the Prime Meridian that point is located.

The Prime Meridian is assigned the value of ${0}^{\circ}$ longitude. Now, Earth performs a complete rotation, i.e. ${360}^{\circ}$, in one day, or $24$ hours.

This means that you can find Earth's rotation angle per hour by using

1color(red)(cancel(color(black)("hour"))) * (360^@)/(24color(red)(cancel(color(black)("hours")))) = 15^@"/hour"

So, the difference between the time at the Prime Meridian, which is given as $\text{5 pm}$, and the time at the location of the ship, which is given as $\text{12 pm}$, amounts to a total of $5$ hours.

This means that the Earth rotated by a total of

5color(red)(cancel(color(black)("hours"))) * (15^@)/(1color(red)(cancel(color(black)("hour")))) = 75^@

But what is the ship's longitude, ${75}^{\circ}$ East of the Prime Meridian or ${75}^{\circ}$ West of the Prime Meridian?

To figure this out, you can use the fact that the Sun rises in the East and sets in the West, which is equivalent to saying that the Earth rotates from West to East.

Notice that the time in the ship's position is behind the time at the Prime Meridian, i.e. the position of the sun in the sky at the ship's location corresponds to what the position of the sun at the Prime Meridian was five hours earlier.

This means that the Earth will rotate for another five hours until the position of the sun in the sky see by the ship will match that of the sun in the sky at the Prime Meridian five hours earlier.

Since the Earth is rotating from West to East, it follows that the ship must be west of the Prime Meridian, at a longitude of ${75}^{\circ} \text{W}$.

## How do minerals change without melting?

Geoearth
2 years ago

Pseudomorphism!

#### Explanation:

Cool word isn't it?

This is a really cool way that a mineral can change its atomic structure without melting. But note that the mineral doesn't change its chemical composition in this case.

An example, a mineral such as Kyanite (${\text{Al"_2"SiO}}_{5}$) has three forms which it can exist in depending on the pressure and temperature conditions.

At low pressure (a few kilobars, roughly a few kilometres into earths crust) andalusite is the stable structure and then at higher temperature moderate pressure sillimanite is the stable structure.

So as we change pressure and temperature a different atomic structure becomes stable and the mineral changes.

Another example is diamond. Diamond is simply carbon ($\text{C}$) but expose it to pressures of around 40 kilobars or more (> 100 km into the mantle) then you get diamond!

Though, I wouldn't recommend putting your pencil in the oven for a few weeks to try and make diamond! But expose diamond to some high temperature and pressure (below its stability field) and it might just transform back to graphite!

Above is the stability ranges for the three guys I mentioned above, diamond occurs four times higher than this diagram (more than 120km into our mantle)!

NB: $\text{0.1 GPa " = " 1 kilobar}$

## Assume that the overall size of the earth's crust stays the same. If one plate is pushing away from the plate next to it on one side, what must be happening at the boundary with another plate on the opposite side?

Geoearth
2 years ago

Subduction

#### Explanation:

This is actually the basis for the expanding Earth theory, where some people think that new rock is being made but old rock isn't being destroyed meaning the Earth's radius is growing with time and therefore expanding! Just let me say that this is not true for a number of reasons, the lack of Earth's expanding radius not being the least of them.

But back to your question, we are a closed-system when it comes to talking about rocks, today. Overtime this wasn't the case but at this present time, we are a closed-system. This means everything we make must come from something else. If I want to create new rock then we must melt old rock.

So at a divergent plate boundary (where the plates are pushing away) plates are slowly moving and at the other end (convergent plate boundary) and they are colliding with other plates.

Two different plates such as an oceanic plate and continental plate can collide then subduction can occur. But if two continental plates collide then mountains can form. Though, subduction can still occur in this case but that explanation is for another time!

## How do the relative positions of Earth, the moon, and sun cause the phases, tides, and eclipses, and determine time on Earth?

Kaylee C.
2 years ago

Moon phases are what of the moon we can see from Earth.

Lunar tides are caused by the moon's gravity pulling on the water on Earth. High tide occurs when the moon is directly in line with the body of water in question. Low tide occurs when the body is perpendicular to the force of gravity.

Solar tides are caused the same way as lunar tides, except that the sun's gravity is pulling the water and that they don't tend to be as powerful.

However, when combined with lunar tides, they can create what are known as spring tides, which can be either extremely high tides or extremely low tides. There are also neap tides, which are the opposite of spring tides.

Lunar eclipses are caused by the shadow of the Earth as it passes in between the sun and the moon. The moon can look red because of the sunlight passing through Earth's atmosphere before reaching the moon.

Solar eclipses are caused by the moon passing between the Earth and the sun. Because of the distance between the two, the moon can block out most of the sun, except for a "halo" surrounding it.

These positions determine time on Earth because they're constant.

For example, one rotation of the Earth takes 24 hours, one revolution around the sun takes 365.25 days, etc. This makes it very easy to create a standard system because no matter where you are in the world, this information stays the same.

## Why are fossils formed in sedimentary rocks?

Geoearth
2 years ago

They are not.

#### Explanation:

Ok so there is a little bit of misunderstanding here.

Fossils are never formed in sedimentary rocks, they are only preserved. So the reason we tend to see fossils mainly in sedimentary rocks is because if you have some type of marine life die, it will sink to the bottom and eventually become covered in sediment. This process takes a long time and eventually will make an imprint in the sediment. This imprint can be replaced by other minerals and then the sediment (which has now become a sedimentary rock) can be exposed. Then we will see the fossil in the sedimentary rock.

Though, you can have fossils in igneous rocks, but it is much much harder to preserve. Igneous rocks have a molten temperature of anything from $900 - {1200}^{o} C$ so you can imagine that if anything touches it, it will most likely be melted. Therefore not preserving any evidence that it was even there!

The most common type of fossil in an igneous rock is something we call an enclave. It isn't really a fossil but it is a foreign piece of rock that gets taken up by another molten rock, so you have a main rock with an enclave of a different type of rock.

This is a great example of diorite (darker material) enclaves inside a granite.

If you follow the Link, Ron Wolf has a pretty neat explanation of how this rock formed.

## How can the sevarity of storms be prevented?

James J.
2 years ago

There is a controversial practice known as cloud seeding.

#### Explanation:

Cloud seeding is the process that adds condensation nuclei while also cooling the air to induce precipitation. Usually this is in the form of dry ice. The dry ice is injected into the cloud by rocket or aircraft. The dry ice is much cooler than then the air so the temperature drops. The result is increased condensation and therefore precipitation. They also use things like silver iodide.

When you cloud seed a cloud that normally would not produce precipitation in an area of drought, the benefits are bringing water to where it is needed. The technique can be used in other more controversial ways, although the success is not definitive.

If you seed a cloud early, it is theorized that you can cause precipitation to occur earlier than it normally would. China did this during the 2008 Olympics to prevent rain at the opening and closing ceremonies. End result was no rain at the opening and closing ceremonies, although it is difficult to say if that was entirely because of cloud seeding.

In terms of storms, there has been research and there is plenty of conspiracy theories about cloud seeding hurricanes. The idea is you use cloud seeding to turn a tropical depression into a hurricane. The point of doing this in reducing storm severity is causing the hurricane to lose much of it's energy through precipitation before the storm can really build.

Here is were the controversy comes in. If say the U.S. decides to seed a tropical depression to turn it into a hurricane and have it lose much energy before it reaches the U.S., what about the countries that it goes over on the way, say Haiti for example. It is sort of like giving your bad luck to someone else because you have the science to do it.

Now does cloud seeding work for hurricanes? If you ask many conspiracy theorists they will say yes and that it is going to be used by the military. If you ask actual scientists, they will not say one way or the other because the idea is sound, but there is little proof.

## How does a hurricane finally die down?

Ed Hitchcock
2 years ago

A hurricane dies down when it loses its energy source, which is usually warm water at the surface of the ocean.

#### Explanation:

One of the driving forces of a hurricane is heat energy in oceanic surface waters.

Warm water evaporates more quickly, and warm air rises. As warm, moist air rises, the air gets thinner (less atmospheric pressure), which causes the temperature to drop slightly, which causes some of the moisture to condense as clouds.

That condensation releases heat, which warms it up, which makes it rise, which makes it cool, which makes more condensation, which releases more heat...

So as long as there is warm surface water to feed the hurricane, it is a positive feedback loop, creating stronger and stronger updrafts, which pull more and more air in, generating the hurricane.

If the hurricane wanders northward, it may move into cooler waters, which slow its growth, and eventually reduce its severity. If it moves onto land it loses that warm water source, and so dies down.

The single most important factor in a hurricane losing energy is friction. When the hurricane is over water the friction with the surface of the ocean is minimal. This results in an almost totally unreduced Coriolis effect. The Coriolis effect is the apparent force on wind that prevents air from moving from high pressure to low pressure, and instead causes the air to deflect and the low pressure center does not fill.

When you add friction, which is when the hurricane makes landfall, the wind speed drops and that means that the Coriolis effect is reduced and the winds gradually spiral inward, causing the intense low air pressure at the center of a hurricane to start filling. As the pressure at the center rises the force caused by the pressure differences (pressure gradient force) drops. This causes the wind speed to drop. The whole things becomes a feedback loop and eventually the hurricane will dissipate.

If you ever follow the movement of a hurricane you will notice that without fail the category of the hurricane will drop by 1 almost immediately after it makes landfall. This is also why when a hurricane hits an island the storm often does not dissipate, as it is not over the area of friction for long enough.

## What is the composition of the Earth's core?

Mr. Doc
2 years ago

At the centre of the Earth is the core, which has two parts-
1. The Solid Inner core.
2.The Liquid Outer Core.