  With the ATNF Mopra telescope we are performing a survey in the 12CO(1-0)
line to map the molecular gas in the Large Magellanic Cloud (LMC). For some
regions we also obtained interferometric maps of the high density gas tracers
HCO+ and HCN with the Australia Telescope Compact Array (ATCA). Here we discuss
the properties of the elongated molecular complex that stretches about 2 kpc
southward from 30 Doradus. Our data suggests that the complex, which we refer
to as the ``molecular ridge,'' is not a coherent feature but consists of many
smaller clumps that share the same formation history. Likely molecular cloud
formation triggers are shocks and shearing forces that are present in the
surrounding south-eastern HI overdensity region, a region influenced by strong
ram pressure and tidal forces. The molecular ridge is at the western edge of
the the overdensity region where a bifurcated velocity structure transitions
into a single disk velocity component. We find that the 12CO(1-0) and HI
emission peaks in the molecular ridge are typically near each other but never
coincide. A likely explanation is the conversion of warmer, low-opacity HI to
colder, high-opacity HI from which H2 subsequently forms. On smaller scales, we
find that very dense molecular gas, as traced by interferometric HCO+ and HCN
maps, is associated with star formation along shocked filaments and with rims
of expanding shell-like structures, both created by feedback from massive
stars.
