7 Oceanic TrencH-Oceanic trenches most likely found at the convergence of two oceanic plates e.g.) Mariana Trench – deepest part of ocean (6.8 mi)
8 Volcanic Arcs-Volcanic Arcs (chains of volcanoes in arc shape) are often formed at oceanic-continental convergent plate boundaries e.g.) Aleutian Islands in Alaska
9 Pacific ring of fire-Majority of crustal activity on Earth is centered about the Pacific Ocean. It’s called the Pacific Ring of Fire. This is where the majority of Earth’s active volcanoes are located.
10 VOLCANIC OUTGASSING-As interior of Earth became hotter, heat caused certain elements to rise to surface in volcanic rock (gases like carbon dioxide, sulfur dioxide, chlorine, ammonia, methane) in early history. -First atmosphere on Earth: mostly Hydrogen gas and He -Photosynthesis added oxygen to atmosphere, but much later in Earth’s history
11 Earth’s current atmosphere Percentage of Elements in Earth’s Atmosphere: N2 78% O2 21% Ar 0.9% CO % & others in trace amounts. -Water vapor (H2O) is also is found in varying amounts depending on the climate (0- 7%).
12 Check your understanding Which element constitutes the highest percentage of mass in Earth’s crust?Which type of plate boundary often forms volcanic arcs?Which type of plate boundary would you expect to find a trench?Where is the majority of Earth’s crustal activity centered around?What is the upward folding of rock called?Which two elements most likely composed the first atmosphere on Earth?List the three most prevalent elements in Earth’s crust in order from least to greatest.What process caused gases like CO2, SO2, NH3, and CH4 to form in earth’s early history?What element is extracted from bauxite?Which element is the most abundant in Earth’s atmosphere?