As part of the volcanic eruption of Mount St. Helens in 1980, there was a large horizontal blast and accompanying landslide that had a horizontal force of about 3.4 x 1021 N that lasted for about 2.5 minutes. Calculate the angular impulse this generated if Earth's radius is 6371 km. Explain why this did not have a measurable effect on Earth's angular momentum (L = 5.9 x 1033 kg.m²/s).