The park's oldest rocks were produced when plate movements subjected sea sediments to intense pressure and heat. The resulting metamorphic rocks (schist and gneiss) are estimated to be 1.8 billion years old. Later, large intrusions of hot magma finally cooled about 1.4 billion years ago to form a core of crystalline igneous rock (mostly granite). Paleozoic Era. During the long Paleozoic Era, the park area frequently submerged, lifted up and eroded.
[{"rock_types": "schist", "era_formed": ["Paleozoic Era", "Paleozoic Era. "]}]
[{"rock_types": "metamorphic | igneous", "era_formed": "Paleozoic"}, {"rock_types": " igneous", "era_formed": "Paleozoic"}] [{"rock_types": "schist ", "era_formed": "1.8 billion years old"}, {"rock_types": "gneiss", "era_formed": "1.8 billion years old"}, {"rock_types": "granite", "era_formed": "Paleozoic "}] [{"rock_types": "schist", "era_formed": "Paleozoic Era. "}] [{"rock_types": "schist", "era_formed": "Paleozoic Era"}] [{"rock_types": "metamorphic| igneous", "era_formed": "n/a"}, {"rock_types": "n/a", "era_formed": "Paleozoic "}] [{"rock_types": "schist", "era_formed": "n/a"}, {"rock_types": "gneiss", "era_formed": "n/a"}, {"rock_types": "granite", "era_formed": "n/a"}]