Three main types of stresses affect the Earth — tensional, compressive and shear. These stresses are responsible for triggering earthquakes and contributing to other geological events, such as landslides. Ultimately, it is these stresses that sculpt the face of the Earth, creating new landforms and restyling the outlines of continents.
Stress is defined as a force exerted over an area. In geology, stresses relate to tectonic plates, enormous slabs of rock that lie underneath all of the world’s landmasses and oceans. Tectonic plates aren’t motionless, however; they shift positions and in doing so, stress builds up along their borders with other plates. If the stress is not equal from all directions — which it often isn’t — rocks can bend, twist and break. This often happens along fault lines at the edges of plates, which is why earthquakes tend to occur in these zones. The three types of stresses correlate with the three types of tectonic plate boundaries.
Tensional stress, sometimes known as extensional stress, stretches and pulls rocks apart. This type of stress occurs along divergent plate boundaries, where two tectonic plates are tearing away from one another. A prime example of tensional stress is the mid-Atlantic ridge, where the plates carrying North and South America are moving west, while the plates carrying Africa and Eurasia are moving east. Tensional stress can also occur well within an existing plate, if an existing plate begins to split itself into two pieces. This process, known as rifting, has been taking place in parts of eastern Africa.
Compressive or compressional stress squeezes rocks together. The opposite of tensional stress, compressive stress happens at convergent plate boundaries, in which two tectonic plates are plowing into each other. Powerful earthquakes tend to strike areas where compressive stress is at work, such as in Chile where the Nazca and South American plates are smashing into each other, or near Japan where the Eurasian plate and Philippine plates are ramming against one another.
Shear stress occurs at boundaries where two plates are sliding sideways past one another, like cars traveling in opposing lanes on a highway. Friction between the plates grinding past one another produces the stress. Shear stress is associated with transform faults, which may also be called strike-slip or slip-strike faults. Perhaps the most well-known example of shear stress is the strike-slip fault known as the San Andreas in California.
A compressed nerve is a physical obstruction of the nervous system, which prevents a correct response between the brain and the affected area. This causes symptoms such as throbbing pain, muscle weakness, mild swelling, spasms, numbness and tingling.
A compressed nerve can happen mostly due to an irregularly formed fibrocartilage due to aging, but other causes include traumatic injuries, the degeneration of a disc in the back that presses on the nerve or conditions such as rheumatoid arthritis.
Although compressed nerves can occur throughout the body, they are much more common in the upper part of the body, especially in the neck, spine, elbows and wrists. In many cases nerve compression may be a temporary condition that can be cured without long-term repercussions.
The pain usually gets worse during the night, so the person suffering from a compressed nerve tends to have sleep disorders. As the pain is constant it is very difficult to find a sleeping position that relieves.
Sleeping on your back puts pressure on the spine and neck, this compresses the nerves and can cause the worsening of this condition. Similarly, being overweight is a factor that greatly increases the risk of suffering from it.
Once you are diagnosed with a compressed nerve, the treatment will surely be a combination of rest, physical therapy and sometimes pain medication. In very specific cases, the doctor may recommend surgery, but always as a last resort.
If you suffer from a compressed nerve make sure you get enough rest, use as little as possible the affected part of the body, eat foods rich in potassium and calcium and especially take care of your posture.
Avoid as much as possible staying prolonged periods of standing. While sitting it is important to keep your back supported and straight, a soft backrest or cushion can be very useful.
To sleep on the side, it is necessary to use a pillow to keep the head and neck aligned and another between the legs . If you sleep on your back, use a pillow under your knees .