There are many theories as to why the TITANIC broke between the third and fourth funnels. Some say that because there was an air shaft, the strain from being so high up and the weight of the engines, the ship broke. Another theory is that the steel was weak there but that's improbable. Another is that the expansion joint in the middle of where the break-up occured had cracked under the pressure and the crack increased as the stern rose higher. What's interesting is that the TITANIC's sister ship Britannic, was improved in it's expansion joint which makes you think if they knew that the expansion joint was what caused the break-up. Another idea is that the stern bent because of the high angle and the weight of the engines and it caused the two to separate. The survivors of the sinking were unclear. Some said that it didn't break apart while others said it did. The conclusion was that the ship sank intact until it's discovery when Robert Ballard discovered the TITANIC split apart. Why the TITANIC broke apart is still inconclusive today.