Deep cracks beneath the waterline led to parts of the 80-year-old harbour wall collapsing in 2012.

BBC: Weymouth harbour wall: Warning over repair noise

This time, deep cracks have appeared in the Iranian leadership as former colleagues battle it out for the future of the Islamic republic.

ECONOMIST: As Iran simmers what will become of the protest movement?

If prices were to go much lower, deep-seated supply side political cracks would become very visible, (very quickly) in places such as Russia, Venezuela, Iraq, Libya, Yemen, Sudan, Libya and Algeria.

FORBES: Oil Memo To President Obama: Go Easy On Iran

They are also trying to understand the role that deep seas trenches play in earthquakes - these cracks in the sea floor are formed at the boundary of two tectonic plates and some believe the push and pull taking place deep underwater could be the cause of major earthquakes, such as the 2011 quake that resulted in such devastation in Japan.

BBC: James Cameron back on surface after deepest ocean dive

With EGS, holes are drilled deep into hot rock and water is injected into the cracks.

FORBES: Magazine Article

Fears are growing about cracks in the Chinese economy, and Asian markets are deep in the red today to start the fourth quarter.

FORBES: Is October Setting Up To Be A Bear Killer Again?

The more it cracks down on and exposes the corruption, the more the people will be reminded of just how deep it goes.

BBC: China turns against official extravagance