Earth was created by God for a special purpose, to be a home for the human beigns, whom He created in His own image.
Earth's perfect distance from the Sun, allows for temperatures "just right" for life. If it was a little farther, we would freeze to death. If it was a little closer, we would melt from heat. Also, Earth's ozone layer in conjunction with its magnetic field blocks harmful solar radiation, allowing us to survive that radiation. Besides beign a home for human beigns, Earth is also home to millions of kinds of plants and animals. These come in all shapes and sizes. They all interact with each other in most intricate ways. Existence of one form of life requires concurrent existence of other forms of life. The chemical composition of Earth's atmosphere, as well as abundace of water, minerals, and plants, keeps all breathing organisms alive. Any changes in the amount of these resources would be catastrophic.
Shape
The Earth is almost a sphere, with a slight bulge around the equator. The diameter at the equator is 43 km larger than the diameter from north to south pole. This bulge is caused by Earth's rotation. The average diameter is about 12,742 km. The tallest mountain on Earth is Mount Everest, at 8848 m above sea level. The depest point is the Mariana Trench in the Pacific Ocean, at 10,911 m below sea level.
Chemical Composition
The mass of Earth is approximately 5.98X10^24 kg. It consists of the following elements: iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%); other elements (1.2%). The enterior of the planet is not known for sure, because we don't know of anyone who drilled through it deeper than a few kilometers, and because oceans fill just a tiny portion of the Earth's crust. All the details about the Earth's core are derived from indirect measurements. According to the current theory, this crust consists of more than 47% oxygen. The other 52+% would be many other elements from the Periodic Table, with silica and alumina beign the most common compounds.
Internal Structure
Unlike the other planets, the Earth's core is divided into distinct outer and inner parts. The outer core is a silicate solid crust. This crust varies from 6 km deep under the oceans, to 30-50 km deep under the continents. At the top of this layer is the soil layer, that allows plant life to grow on our planet.
The inner core is a highly viscous solid mantle. According to the plate-tectonic theory, the inner layer is divided into the lithosphere and the asthenosphere. Lithosphere is comprised of the broken-up tectonic plates. While the asthenosphere is like oil on which these plates move. The plate-tectonic, or the Pangea theories are debated in the creation science circles. Some creation scientists would point out that if you lower the ocean level only by a little bit, (which was very likely the case before the flood), all the continents would be connected, forming a giant super-continent. However, the Earth's crust have been broken at some time, (possibly during the Flood), because earthquakes are indications of shifting of the crust's plates, which keep trying to settle into lowest position, rubbing against each other in the process.
Heat
Most of the heat produced by the Earth (80%) is caused by radioactive decay. At the center of the planet, the temperature may be up to 7,000 K and the pressure could reach 360 GPa.
Surface
Most of the Earth's surface (70.8%) is covered with water. The surface submerged under the ocean consists of many mountains and volcanoes, including the globe-spanning mid-ocean ridge. Currently, 13.37% of the land-surface can be used to grow crops. Only 4.7% can support permanent crops. However, only 40% of that land is currently used for cropland or pastures. The Earth is almost a flat surface when compared to the thickness of its crust. The mean height of land above sea level is only 840 m.
Hydrosphere
Hydrosphere consists primarily of ocean water, but also includes inland seas, lakes, and rivers, as well as underground water down to 2,000 km below to sea level. The mass of the ocean is approximately 1.35X10^18 metric tons, or about 1/4400 of the total mass of the Earth. The ocean covers an area of 3.618X10^8 km2 with a mean depth of 3,682m, resulting in an estimated volume of 1.332X10^9 km3. If all land on Earth was spread evenly, the water would cover the planet to more than 2.7 km deep. Most water, 97.5%, is saline, and only 2.5% is fresh water good for drinking. 68.7% of that fresh water is in the form of ice at the polar ice caps.
The average salinity of Earth's oceans is about 35 grams of salt per kilogram of water. The ocean is a reservoir of dissolved atmospheric gases. on which many aquatic life forms depend for survival. The ocean also serves as a giant heat reservoir. Shifts in the oceanic temperature distribution can cause significant weather shifts.
Atmosphere
Earth's atmosphere is composed of 78% nitrogen and 21% oxygen, with insignificant amounts of water vapor, carbon dioxide, and other gaseous molecules.
The ozone layer helps block ultraviolet radiation from the Sun, permitting life on this planet. The atmosphere captures small meteorites and burns them before they reach the land. It also is responsible for what is known as "the greenhouse effect"; where molecules in the atmosphere capture thermal energy emitted from the ground, raising the average temperature on the planet. Without the greenhouse effect phenomenon, the average temperature on the planet would be -18C and life would not survive.
But the atmosphere does not seem to provide the protection it used to provide. It seems to have been significantly altered during the Great Flood. Most creation scientists suggest some variation of a "water canopy" theory, some sort of a water layer previously existing above the atmosphere which provided much better protection from the Sun's radiation, as well as keeping the planet's temperature nearly uniform throughout the globe. Such a protective layer of water would greatly slow down human aging process, and extend the human life-span to great ages described in the first chapters of the book of Genesis. This layer may have been one of the sources of water to flood the world; the second source beign the water from the "fountains of the deep". Whatever this protective layer was, it is gone after the flood, because the human life-spans sharply decreased immediately after the Great Flood.
Weather
Earth's atmosphere has no definite boundry. Instead, it just keeps getting thinner as you move farther away from the surface of the Earth. 3/4 of the mass of the atmosphere lies within 11 km from the planet's surface. This layer is called the troposphere, and it is this layer that drives weather and climate on the planet. Energy from the Sun heats up this layer and the surface below, causing air to expand. The resulting lower density air rises, and the colder, heavier air above, sinks, causing atmospheric circulation responsible for weather patterns on the planet.
When warm air containing evaporated water molecules rises, and the atmospheric conditions are right, the water condenses and falls to the ground as percipitation.
The mean annual air temperature decreases by 0.4C per degree of latitude away from the equator. That is due to the fact that the Sun's rays hit the atmosphere at steeper angles as you move away from the equator, and have to go through thicker columns of atmosphere.
Geology
Earth's surface features change all the time. Throughout history, catastrophic events wiped out entire cities and civilizations, changed the flow of rivers, locations of continents, and the size of the polar ice caps. According to the Biblical account, our planet was once completely covered with water, in a catastrophic global flood, which destroyed the first human civilization, leaving only 8 people. This flood had tremendous effects on the geology of our planet, such as carving out huge canyons, raising some mountains, and lowering others, as well as breaking up the initial unified super-continent into smaller modern continents.
Satellites
Earth has only one satellite, known as the Moon. According to biblical records, the Moon was created on the same day as the Sun and the stars. The purpose for its creation was to create a guide for measurement of time during the nights, while one of Sun's purposes was to serve that mission during the days. Interestingly, the Moon was strategically placed at just the right distance from the Earth to appear to us to be the same size as the Sun. While the Sun is 400 times farther from us than the Moon, the Moon is 400 times smaller than the Sun. When you cancel that out, both the Sun and the Moon appear to be the same size to us, providing equal size guides for us during the day, as well as during the night.
The Earth interacts with both the Moon and the Sun gravitationally. Gravitational pull from the moon causes changes in the ocean level on Earth, known as tides. The Moon also helps stabilize Earth's rotation, and gradually slows down the planet's rotation. The tidal interaction between the Earth and the Moon, causes the Moon to recede from us a little bit each year. The current rate is 38 mm per year.
The Moon's rotation period is the same as the time it takes to orbit the Earth. For that reason, the Moon always shows us the same face. As the Moon orbits the Earth, different parts of the Moon are illuminated by the Sun, causing lunar phases.
Life
Earth has over 7 billion human beigns. They are very similar to each other, yet each have their own unique personality. Same uniqueness goes for plants and animals. Human beigns are grouped into around 200 sovereign states. This number constantly fluctuates, as people merge with each other and split from each other. Most modern human beigns believe in one God. Some continue to believe in many gods, as during many centuries prior to the birth of Jesus Christ. Some believe the first two groups created gods to fill a gap in their imagination.
Human beigns are highly social creatures. They constantly interact with each other. Sometimes these interactions are peaceful, such as resolving conflicts through diplomacy, trading, exchanging ideas, and organizing a multitude of different social gatherings. However, during almost every year of Earth's existence, people resolve their conflicts with wars and other forms of violence. This is a result of people's divergence from the rule of God, the Creator, and the fall of the human nature into sin. This sin is causing suffering not only for the human beigns, but for all plants and animals on the planet as well.
The Future
The Creator of the Earth and all life on it, promised to restore this planet to its original design. Peace, order, and balance will be restored. Suffering will be forgotten, and the human race strengthened by the temptations and suffering of this era, will live in perfect happiness.
Sources:
http://en.wikipedia.org/wiki/Earth
Images courtesy of NASA