Climate changes arise when the Earth has an energy imbalance which causes the Earth to gain or to lose heat.
Looking at the past climatic changes helps us to understand how the climate of the Earth reacts to external forcings. The study of paleoclimates have enabled us to understand that the climate of the Earth can shift between different climate states in just a few number of years or a few decades. The studies of the past climate changes also enables us to understand how humans might have affected the climate in the past and in the present day.
As the data obtained from these observations is not clearly direct, we cannot consider it to be highly authentic. As we know, many a times, scientists form theories in a way that benefit their own perspectives.
They would most likely be metamorphic. "Lava" refers to magma (molten rock) that has reached the surface, igneous rock is sourced from magma and lava, and sedimentary rocks are formed at the Earth's surface.
