1. Forces Shaping Earth Notes Mrs. Seay 6 th Grade Science

2.  Geologists use earthquakes and surface rocks to indirectly observe Earth’s interior

3.  1. Seismic waves change speed and direction depending on the density and material they travel through.

4.  2. Forces bring rocks formed deep within Earth to the surface.

5.  3. Evidence suggests that Earth is formed of different materials in layers.

6.  B. Earth has four layers.

7.  Inner core—dense iron core; very hot and dense.

8.  Outer core—molten metal above the inner core

9.  Solid layer that flows slowly like putty is the mantle.

10.  Outermost layer is the crust.

11.  C. Earth’s structure—theories based on physical properties of density, temperature, and pressure that change with depth.

12.  Earth’s moving plates are sections of the lithosphere, the rigid upper part of the mantle and crust.

13.  Plate boundaries are edges where plates meet.

14.  Tension can pull plates apart, resulting in new lithosphere forming in the gaps.

15.  Colliding plates could cause mountains to form as rock crumbles and folds.

16.  Subduction occurs when a denser plate sinks underneath a less dense plate.

17.  Shearing causes faults and earthquakes as two plates slide past each other.

18.  Plate movement theory—convection in the mantle circulates material and moves plates.

19.  Ridge-push at mid ocean ridges causes plates to slide down the slope.

20.  Slab-pull happens as plates move away from mid-ocean ridges and become denser.

21.  Mountains form in different ways.

22.  Fault-block mountains form from huge tilted blocks of rock separated from surrounding rock by large faults.

23.  Folded mountains form by compression forces folding rock layers.

24.  Upwarped mountains—forces push up Earth’s crust and allow the sedimentary rock to erode, leaving igneous or metamorphic rock.

25.  Over time, layers of lava can form a cone-shaped volcanic mountain.

26.  Hot spots formed by plumes of magma in the mantle can cause underwater volcanic mountains.

27.  Isostacy principle in dicates Earth’s crust and lithosphere float on the upper mantle.

28.  Earth’s crust is thicker under mountains.

29.  When mountains erode, the crust rises because the weight has been removed.