Earthquakes cause Volcanoes

As the crust changes and moves in a major earthquake, fissures or cracks can form that may act as pipelines for magma and future volcanoes. This is harder to monitor and test and is an area of active research. There are 13 volcanoes erupting today (1/9/19) on the globe and most if not all are caused by earthquakes.  That number changes month to month. 

A powerful eruption started at Manam volcano, Papua New Guinea around 03:00 UTC on December 8, 2018. Heavy ashfall is falling on the island, blocking out sunlight.

Volcanic ash rose up to 13.7 km (45 000 feet) above sea level, according to the Darwin VAAC, forcing authorities to raise the Aviation Color Code to Red. Heavy ashfall is blocking out sunlight on the island, locals report.
New evidence shows that very large earthquakes can trigger an increase in activity at nearby volcanoes. An analysis of records in southern Chile has shown that up to four times as many volcanic eruptions occur during the year following very large earthquakes than in other years. This 'volcanic surge' can affect volcanoes up to at least 500 km away from an earthquake's epicenter.
When a volcano erupts, the pressure of the rising magma forcing its way through the crust to the surface will often trigger earthquake activity. Scientists have been able to demonstrate this link and also know what type of earthquake to look for.
Colliding plates

Where plates come into contact, energy is released. Plates sliding past each other cause friction and heat. Subducting plates melt into the mantle, and diverging plates create new crust material.

Subducting plates, where one tectonic plate is being driven under another, are associated with volcanoes and earthquakes. This activity is focused along the edge of the plate boundary where two plates come into contact, forming regions such as the Pacific Ring of Fire – a chain of earthquake and volcanic activity around the edge of the Pacific Ocean – which generates 75% of the world’s volcanoes and 80% of the world’s earthquakes.
Earth Quakes occur along the plate margins as long faults such as the San Andreas fault. Other related faults branch off at predictable angles along the fault in what are called conjugate faults and fractures. These occur at 120 and 60 degrees and can form swarms or fault systems such as the one that runs under Los Angeles County.

 Now compression due to plates pressing against one another (faults under the Himalayas), or moving laterally alongside each other (Pacific Plate and N. American plate along the San Andreas), or subduction boundaries where one plate is moving under another.

This subduction forms not only earthquakes but volcanoes, as the sub-ducted plate melts and the water in the rock and sediment acts as a flux liquefying the rock allowing it to rise into the overlying plate forming volcanoes. The volcanoes from the Andes all the way to the Aleutian Islands are an example.

Sub-ducting plates form the volcanic islands of Japan and the volcanoes in Italy, Vesuvius and Mt, Etna on Sicily are examples.

The volcanoes of Iceland and its earthquakes are due to a spreading margin. The Atlantic plate is pulling apart and Iceland is forming from volcanic flows along the mid-Atlantic ridge, or boundary.
Nature. We have to have volcanoes to release pressure from the earth’s core. If we didn't have volcanoes, our Earth will become so hot and it will break in half. We have to have volcanoes to get rid of pressure, gas and toxic poisons. Volcanoes keep our Earth in line. Without them, we will die if the volcanoes didn't release their lava and volcanic ash poisons. Volcanoes and earthquakes are nature.

 Earthquakes occur; they are not formed. Earthquakes often occur before and during volcanic eruptions. Suggest that the questioner, if serious, actually do some research into volcanoes, earthquakes and tectonic plates, you might start with the “ring of fire” around the Pacific Ocean rim.
As many as ten million underwater volcanoes

Some of the newly-found volcanoes rose almost 1½ miles above the seafloor. Even then, their peaks remained about 1½ miles below the water’s surface. They’re packed into a relatively small area about the size of New York state.

We have no idea how many volcanoes may be lurking beneath the seas. What we do know, is that they are pumping awesome amounts of re-hot basalt – up to 1,200ºC (2,200ºF) hot – into the inky black water.

Global-warming alarmists scoffed. A mere 11,000 submarine volcanoes could not possibly be heating the seas. Impossible. After all, the oceans cover 71 percent of our planet.

But the number of underwater volcanoes kept climbing. By 2005, NASA was forced to admit that there might be one million submarine volcanoes. As many as 75,000 of those underwater behemoths soar half-a-mile above the surrounding seafloor and several thousand of those, in turn, might be active.

Even so, global-warming alarmists never wavered. One million underwater volcanoes were not enough to heat the seas.