The dynamic of these huge events is pretty well understood as being related to Mantle plumes which are superheated columns of rock (not magma) rising from close to the Core/Mantle interface. They rise through the Mantle as relatively narrow features, but as they reach shallower levels they form mushroom-cloud shaped bodies of rock. The reduction in pressure is enough to partially melt the head of the plume; meanwhile the impact of the plume on the lithosphere causes it to bulge upwards, thin and fracture allowing the magma to pour out as flood basalts.
As you say, the Deccan is probably linked to the extinction of the dinosaurs; a massive decline in biodiversity (especially in the oceans) and a wildly-changing climate and acidified rainfall were all occurring long before part of Mexico was turned into a crater. Right now, that plume is driving the volcano on Reunion in the Southern Indian Ocean - but the good news is that once the head of the plume has been exhausted, the long tail only provides a relative trickle of melt.
The most productive plume on the planet right now is the plume that created the Antrim Basalts in Northern Ireland is now driving most of the volcanism in Iceland (the MidAtlantic Ridge is a relatively small contributor to Icelandic activity); but the most impressive is the one under Afar in Ethiopia which is pushing the whole of East Africa more than a kilometre into the sky and driving the Africa Rift Valley - although it probably isn't strong enough to rift Africa into two.
In theory, we could see any emerging plumes long before they arrive on the surface through technologies such as seismic tomography and their effect on local gravitation; but the good news is that there is no obvious threat from a new plume for the immediate geological future.
The threat is from the tails of existing plumes, which although they only ten to produce a fraction of a cubic kilometre of melt each year, can occasionally produce monstrous volumes of magma - such as our old friend the Icelandic plume which produced 18km3 in the Eldgyá eruption of 939CE; depressed Northern Hemisphere temperatures by 2C and probably inspired the Viking idea of Ragnarok; and then vomited up a further 14km3 from nearby Lake during 1783-84; creating a famine that killed a quarter of Icelanders, poisoned more than 20,000 people in England and probably contributed to a complete collapse of the Indian and Chinese monsoons. If they were to happen today, the death toll across the World could be unimaginable.
Just to put those into context, after 65 million years of erosion, the Deccan contains more than one million km3 of lava. Magnetic evidence suggests most of it was erupted within a span of 20,000 years which included several prolonged episodes of inactivity. A Deccan-like eruption would be the end of us.
It would however be a beautiful way to go....