What was the altitude of the yield of 1.4 megatons?
CREATE TABLE table_148578_1 (altitude__km_ VARCHAR, yield__approximate_ VARCHAR)
SELECT altitude__km_ FROM table_148578_1 WHERE yield__approximate_ = "1.4 megatons"
### Context: CREATE TABLE table_148578_1 (altitude__km_ VARCHAR, yield__approximate_ VARCHAR) ### Question: What was the altitude of the yield of 1.4 megatons? ### Answer: SELECT altitude__km_ FROM table_148578_1 WHERE yield__approximate_ = "1.4 megatons"