Jan 6 (Reuters) - A growing number of emerging market currencies have fallen to record lows against the U.S. dollar, which hit an 18-year peak in December, and several others are approaching them.

Weakness is widespread, incorporating China's yuan, India's rupee, Russia's rouble, Brazil's real and South Africa's rand, yet goes far beyond the higher profile currencies of BRICS nations.

Turkey's long suffering lira is regularly setting news lows, Mexican and Chilean pesos and South Korea's won have slumped, and all-time lows are close for Indonesian Rupiah, Philippine peso and Malaysian ringgit.

Currencies have moved beyond lows previously reached in times of crisis, yet there is little to suggest that investors are overly concerned now.

Retreats for equities and crypto currencies are merely froth off the top of huge rises and moves in major currency markets are unfolding sedately.

This may not last if slides for emerging currencies accelerate as they fall further into uncharted waters as liquidity diminishes

Should this spur demand for the safety of the world's reserve currency, the reactive calm of major markets could be shattered with a disorderly adjustment phase and a big rise in volatility.

Unless emerging nations allow FX reserves to fall, which may spur risk aversion anyway, interventions to slow the falls of their currencies will likely boost the dollar against major currencies - in particular the euro.

That is because central banks usually buy back dollars sold versus liquid major currencies in order to maintain the size of reserves.

Dollars are more often purchased versus the euro, but also yen and pound, which has created a vicious circle that has underpinned the world's reserve currency during a 41% gain in value since 2011.

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(Jeremy Boulton is a Reuters market analyst. The views expressed are his own, editing by Ed Osmond)

((jeremy.boulton@thomsonreuters.com))