How do we know a dramatic event occurred when we see curved or tilted rock layer

Question

How do we know a dramatic event occurred when we see curved or tilted rock layers? because the text book says so because the law of original flatness says that rocks start out flat because the law of original horizontality says sediments are deposited in flat, parallel, horizontal layers geologists decided What causes load casts and sand volcanos? rocks are heavy load casts form when high density sand layers over low density mud layers where both are saturated and sand volcanoes form when high density (dry) sediment or soil layers are above a low density saturated sand layer load casts form when low density sand layers over high density mud layers where both are saturated and sand volcanoes form when low density (dry) sediment or soil layers are above a high density saturated sand layer What do all of the types of unconformities have in common? they are confusing they all represent a continuous rock record (no missing time) they are all ways that valleys and mountains form they all represent a gap in the rock record (missing time) What is a disconformity and what is the "catch phrase" for remembering what it is? rock is missing between 2 parallel rock layers, the rock is lost in time like the disco the rock below the contact is crystalline while the rock above it is sedimentary because they are non-similar rock types the rock above and below the contact are at different angles, because angles the rock below the contact is shaped like hills and valleys, because it has hills and valleys like a buttress around a castle What is the difference between a dike and a sill? a sill is horizontal like a window sill and a dike is vertical like a dike along a river a sill is vertical and a dike is horizontal a sill is parallel to the existing bedding planes and a dike goes across the existing rock a sill cuts across the existing rock, sometimes in a swarm, and a dike is parallel to the beds, squeezed between them

Explanation / Answer

1. Since the law of original horizontality states that in an undeformed strata, beds are deposited in a flat, parallel and horizontal layers. If we found tilted or curved rock layers it means that some kind of dramatic events like folding, folding and other deformation events have occured which resulted in present tilted form of the rock layers.

2. Load casts are the irregular bulbous features formed when denser material sinks into less dense sediment. They occur on the soles of sandstone beds that overlie mudstones or shales. They are formed by deformation of uncompacted, hydroplastic mud beds due to unequal loading by overlying sand layers. The uncompacted mud having excess fluid pressure or muds are liquified externally generated shock or by the weight of overlying mud. Whereas sand volcanoes are found form when sand is ejected onto the surface in the form of cone from a central point. It forms when water under pressure boils up and wells up through the sand beds. So load casts form when the high density sand layers are over the low density mud layers and both are saturated. Whereas sand volcanoes are formed when high density sediment or soil layers are above a low density saturated sand layer.

3. The unconformities represent the gaps in the rock record. They are the contacts where the two rocks are of different ages. They may represent episodes of erosion, crustal deformation and sea level variations.

4. Disconformity is an unconformity in which both the rocks ypes are different. This is the contact at which the above rock is sedimentary and the underlying rock is crystalline.

5. Dikes are discordant igneous structures which cross cut the country rocks and lies across the existing rock whereas sills are concordant igneous structures which are intruded parallel to the bedding plane of the preexisting rock.

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