CREATE TABLE table_2657 ("Outcome" TEXT, "Year" FLOAT, "Championship" TEXT, "Surface" TEXT, "Partner" TEXT, "Opponents in the final" TEXT, "Score in the final" TEXT)

What is the surface made of if the year is 1979 and the championship is US Open?
SELECT "Surface" FROM table_2657 WHERE "Championship" = 'US Open' AND "Year" = '1979'
SELECT "Surface" FROM "table_2657" WHERE "Championship" = 'US Open' AND "Year" = '1979'