Those showers are present at and below the earth's surface as muons. This link looks kind of nice: https://cosmic.lbl.gov/SKliewer/Cosmic_Rays/Muons.htm https

Those showers are present at and below the earth's surface as muons. This link looks kind of nice: https://cosmic.lbl.gov/SKliewer/Cosmic_Rays/Muons.htm https://cosmic.lbl.gov/SKliewer/Cosmic_Rays/Muons.htm Muon imaging exploits these muon showers. https://www.sciencenews.org/article/muon-subatomic-particle-volcano-pyramid-physics https://www.sciencenews.org/article/muon-subatomic-particle-...