# Below the surface revision

Resource sharing Volcanic landforms There are variations in the form, frequency and type of volcanic eruption. These are related to the different kinds of plate margin, emissions and lava. Intrusive volcanic landforms When magma is forced to the surface only a small amount of the mass actually reaches that level. Calculating Potential Fields A field is a region of space where forces are exerted on Below the surface revision with certain properties.

In this and subsequent sections three types of field are considered: These three types of field have many similar properties and some important differences.

There are key definitions and concepts that are common to all three types of field. Radiant energy such as light has mass and so is affected by gravitational fields. Gravitational fields Newton realised that all objects with mass attract each other. This seems surprising, since any two objects placed close together on a desktop do not immediately move together.

The attractive force between them is tiny, and very much smaller than the frictional forces that oppose their motion. Gravitational attractive forces between two objects only affect their motion when at least one of the objects is very massive.

This explains why we are aware of the force that attracts us and other objects towards the Earth — the Earth is very massive. The lines show the direction of the force that acts on a mass that is within the field. This diagram shows that: The force exerted on an object in a gravitational field depends on its position.

The less concentrated the field lines, the smaller the force. If the gravitational field strength at any point is known, then the size of the force can be calculated. Gravitational field strength is a vector quantity: Always use the given value for g.

A point mass is one that has a radial field, like that of the Earth. Although the Earth is a large object, on the scale of the Universe it can be considered to be a point mass. The gravitational field strength at its centre is zero, since attractive forces pull equally in all directions.

Beyond the surface of the Earth, the gravitational force on an object decreases with increasing distance. When the distance is measured from the centre of the Earth, the size of the force follows an inverse square law; doubling the distance from the centre of the Earth decreases the force to one quarter of the original value.

The variation of force with distance from the centre of the Earth is shown in the diagram. Remember that two objects attract each other with equal-sized forces acting in opposite directions. It can also be used to calculate the strength of the gravitational field due to a spherical mass such as the Earth or the Sun.

A negative sign is sometimes used on the right-hand side of this equation, following the convention that attractive forces are given negative values and repulsive forces positive values.

It follows from the definition of gravitational field strength as the force per unit mass that the field strength at that point, g, is related to the mass of the Earth by the expression: Gravitational field strength is a property of any point in a field.

It can be given a value whether or not a mass is placed at that point. Like gravitational force, beyond the surface of the Earth the value of g follows an inverse square law. Even when flying in an aircraft at a height of 10 m, the change in distance from the centre of the Earth is minimal, so there is no noticeable change in g.

The radius of the Earth is about 6. The same symbol, g, is used to represent: These are not two separate quantities, but two different names for the same quantity. The units of gravitational field strength, N kg—1, and free-fall acceleration, m s—2, are also equivalent. It is not possible to place an absolute value on the potential energy of any object when h is measured relative to the surface of the Earth.

Two similar objects placed at the top and bottom of a hill have different values of potential energy, but relative to the ground the potential energy is zero for both objects. Absolute values of potential energy are measured relative to infinity. The car at the top of the hill has more potential energy than the one at the bottom, but relative to ground level they both have zero.China wants foreign submarines to stop traveling below the surface in the vast waters it claims By Steve Mollman February 20, Submarines are designed with one primary aim: to travel underwater.

Rights Above and Below the Surface of Land -Historically it was considered that the land owner owned everything above and below the surface of the land. Cuius est solum eius est usque ad coelum et ad inferos was said to apply - meaning whoever owns the soil owns everything up to the heavens and down to the depths of the earth. Jan 01,  · Below the Surface by Karen Harper follows the story of Briana Devon whose twin sister disappears during an underwater dive. The sisters are conducting a scientific experiment concerning sea grass and Briana dives to collect data while her sister Daria remains on board their boat/5(41). Batholiths are formed deep below the surface when large masses of magma cool and solidify.

As the magma cools slowly, large crystals are formed in the rock (e.g. granite).

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Intrusive Volcanic landforms - Ace Geography