Wind-whipped sand dusts cast a thick haze on Seoul and across much of the Korean Peninsula for the second day Friday. All kindergartens and elementary schools in Seoul and nine other cities were ordered closed for the day in the first such measure in history. The Seoul Metropolitan Office of Education said the yellow dusts are feared to be detrimental to the health of students ... causing eye, nose and respiratory illnesses. The "yellow sand" phenomenon also turned day into yellowy dusk in other provinces. Hospitals were crowded with people complaining of eye and respiratory illnesses. Visibility dropped to one and a half kilometers in Seoul and surrounding cities. Pedestrians covered their mouths with a mask. On Thursday and Friday, the yellow dust forced cancellation of dozens of domestic flights at Gimpo Airport in western Seoul. Authorities are advising people to stay indoors to protect them from the dust. Meteorologists blamed severe drought in recent months and deforestation in northwestern China for the yellow dust. Weathermen forecast that the yellow sand phenomenon will subside over the weekend, but a few more would hit the nation this spring. Dust storms blown off the dry expanses of the Gobi Desert desert plain choke the Korean Peninsula every spring, but the Korea Meterological Administration said this year's is the worst in history.